pECTUXCrLUS.] 



MUSEUM OF ANIMATED NATURE. 



271 



fossil species, viz., Area diluvii ; and tliis iatler is 

 figured by Brocchi as Area anliqiuita. Sucli was the 

 confiisicii in which the Area antiquata remained, 

 until cleared up by the celebrated naturalist above 

 alluded to. 



We now pass to the genus Peetiinculus, in vvliich 

 the shell is thick, solid, equivalve, nearly equilateral, 

 entirely closed, with small umbones more or less 

 distant, and an external ligament. The hinge pre- 

 sents a curvilinear row of small narrow teeth, rather 

 numerous and intrant; they are often incomplete 

 under the umbones. 



The animal is rounded and thick, with no tenta- 

 cular filaments on the border of its mantle ; the la- 

 bial appendages are narrow, the foot is large, com- 

 pressed and slit longitudinally. 



Tlie Pectunculi live on sar.dy or muddy bottoms, 

 and move by means of their large powerful foot 

 with considerable dispatch, propelling themselves 

 vigorously along. They are found in depths varying 

 from a few feet to seventeen fathoms: They have 

 no byssus. 



2946. — The Hairy I'ectunxulus 

 {Pectuncidus pllos^is). The term hairy or pilosus is 

 given to this species because the shell is covered 

 with a brown hairy epidermis, giving it a singular 

 appearance. The shell is orbiculate and ovate, 

 with oblique umbones, and marked by decussate 

 striae. It is a native of the Atlantic, and occurs also 

 in the Mediterranean. 



Of this genus M. Deshayes enumerates twenty in 

 his last edition of Lamarck ; but to these must be 

 ad<led three species described by Mr. Broderip in 

 the 'Proceeds. Zool. Soc' 1832, p. 12G, and six 

 species described by Mr. G. B. Sowerby in the same 

 Proceeds, p. 195 et seq. ; all from the western coast 

 of South America, and the islands of the South 

 Pacific Ocean. Several fossil species are recorded. 



The next genus to be noticed is Nucula of La- 

 marck, which is characterized by the shell being 

 rather thick, sometimes nacreous ; subtriquetrous in 

 form, equivalve, but inequilateral ; the umbones are 

 contiguous and curved forwards; the hinge exhibits 

 on each valve a row of numerous small pointed 

 teeth disposed in a line, but interrupted at the 

 umbo. The ligament is to a great extent internal, 

 and is inserted into a small oblique fosset in each 

 valve. 



The animal is rather thick, with the mantle open 

 only at its inferior portion; its borders are entire, 

 denticulated throughout the length of the back, 

 without posterior prolongations ; the anterior oval 

 appendages are long, pointed, and stiff; the posterior 

 stiff and vertical. The foot is large, slender at its 

 root, and expanding into a great oval disc, the bor- 

 ders of which are furnished with tentacular digita- 

 lions. 



Fig. 2947 represents the animal and shell of 

 Nucula Australis. A, the animal ; a a, the mantle, 

 denticulated along the dorsal margin; b, the foot 

 unexpanded ; e e, the two adductor muscles; c, the 

 branchiiB. B, outline of the shell, with the foot of 

 the mollusk projecting. 



The Nuculae generally tenant beds of sandy mud, 

 botii in a;stuaries and the open sea, varying from 

 the surface to sixty fathoms. One species, Nucula 

 Pisura, Sowerby, was found by Mr. Cuming on 

 coarse sand and gravel at various depths from seven 

 to forty fathoms, and N. cuneata from fourteen to 

 forty-five fathoms; hence it would appear that the 

 same species is capable of living under various de- 

 grees of pressure. The same conchologist found N. 

 obliqua at the depth of fourteen fathoms, and at 

 the depth of sixty fathoms. 



2948.— The Beaked Nucula 

 (Xucula rostrata). In this species the shell is ob- 

 long, thin, 1 1 ansversely striated, and produced into 

 a beak-like termination. 



2949.— The Pearlv Nucula 

 (^Nucula mnrgmitacea). The shell is obliquely 

 ovate, trigonal, and rather smooth ; the cardinal 

 teeth are straight and acute, the margin is crenu- 

 lated. 



Referring to Fig. 2949, A represents the interior 

 of the valve, showing the teeth on each side of the 

 hinge, and the cartilaginous pit in the centre ; B, 

 the exterior of the valve ; C, a view of the cardinal 

 teeth, the margin of the shell being towards the ob- 

 server, and enlarged ; D, the shell with the valves 

 closed, showing the umbones. 



M. Deshayes records ten living species of Nucula 

 in his last edition of Lamarck; in the ' Proceeds. 

 Zool. Soc' 18.32, are ten new species from the 

 western coast of South America, described by Mr. 

 G. B. Sowerby ; they formed part of Mr. Cuming's 

 celebrated collection. 



Immediately after the genus Nucula, Cuvier in- 

 troduced the genus Trigonia of Bruguidres, so re- 

 markable for the hinge, which is furnished with two 

 laminae, en chevron, crenulated on each side, and 



received each into two fossets, or rather between 

 four laminae of the opposite valve, also crenulated 

 internally. MM. Qiioy and Gaimard, he adds, have 

 recently discovered a living example of this genus. 

 The animal, like that of area, has the mantle open, 

 without any separate orifice ; the foot is large and 

 compressed, and hook-shaped anteriorly. Accord- 

 ing to M. Deshayes, this genus is evidently near the 

 Nuculae, and the only question is whether it should 

 form part of the family of the Arcadae, or stand by 

 itself as a small but independent family next to it. 



M. Rang describes the shell as thick, nacreous, 

 subtrigonal, equivalve, and inequilateral. The um- 

 bones are rather small, and but little curved ; the 

 hinge is complex and dissimilar ; the right valve 

 having two great teeth of an oblong form, diverg- 

 ing from the umbo, strongly furrowed, and penetrat- 

 ing into two excavations of the same form and 

 equally furrowed on the left. The ligament is ex- 

 ternal. 



One species only, in a living state, is known. 



2950. — The Pearly Tbigoma 

 (Trigonia margaritacea). This rare species has 

 only been found in the seas of New Holland, on 

 sandy mud, ranging in depth from six to fourteen 

 fathoms. It is of moderate size. The shell is sub- 

 orbiculate, nacreous within, and ribbed externally. 

 The ribs are elevate, verrucose, somewhat sharp, and 

 radiating. The margin is plicated. It is the Tri- 

 gonia pectinata of Lamarck. 



The fossil species of this genus are numerous ; 

 they occur in the green-sand, the lias, the upper 

 and lower oolites, and throughout the oolitic series 

 of Phillips and Conybeare. Dr. Fitton records 

 twenty-two or more species, principally from the 

 lower green-sand. The fossil Trigoniae belong to a 

 remote period. " We should,' says Mr. Sowerby, 

 " have been much disposed to doubt the probability 

 of any species occurring in the strata above the 

 green-tand, if Miss Salisbury had not shown us one 

 which she dug out with her own hands at Muddiford. 

 Notwithstanding this fact, the Trigonia may be said 

 to characterize the beds below the chalk, and above 

 the lias." 



With respect to the fossil species of the other 

 genera of the family Arcadae, the following details, 

 the result of no trifling labour and research, are 

 given in the ' Penny Cyclopaedia.' 



" Cvciillwa. Mr. G. B. Sowerby (' Genera ') no- 

 tices the fossil species as numerous ; of these, he 

 observes, one (Cue. crassatina) is described by La- 

 marck, and is found in the neighbourhood of Beau- 

 vais and at Bordeaux, in beds similar to that of 

 Grignon, but in England several species occur, both 

 in the green-sand and in the inferior oolite, and are 

 engraved in Sowerby's ' Mineral Conchology.' Mr. 

 G. B. Sowerby adds, that those of the inferior oolite 

 are also found at Bayeux in Normandy. 



" The number of fossil species (tertiary) recorded by 

 M. Deshayes in his Tables is two. In the last edi- 

 tion of Lamarck the number is six. Dr. Mantell, in 

 his ' Tabular Arrangement of the Organic Remains 

 of the County of Sussex,' notes a CucuUaea in the 

 chalk marl, and adds that M. Brongniart sent him a 

 similar cast from Rouen ; also Cucullaea decussata, 

 from the Shanklin sand (Feversham). 



" Professor Phillips (' Organic Remains of the York- 

 shire Coast') records Cucullaeae oblonga, contracta, 

 triangularis, and pectinata, from the coralline 

 oolite ; elongata from the coralline, Bath, and in- 

 ferior oolite ; concinna from the Oxford clay and 

 Kelloway's rock ; imperialis and cylindrica from the 

 Bath oolite ; cancellata from the Bath and inferior 

 oolite; reticulata from the inferior oolite; and no- 

 tices the occurrence of the form in the Speeton clay 

 and the lias. In the second part (183G) he describes 

 Cucullaea: obtusa and arguta (I3olland). (' Illus- 

 trations of the Geology of Yorkshire.') Dr. Fitton, 

 in his 'Stratigraphical and Local Distribution of 

 Fossils,' in his valuable paper ' On the Strata below 

 the Chalk' (1839), notices the following Cucullaese 

 — carinata (Blackdown) ; costellata? (lower gi-een- 

 sand, Kent ; Blackdown, Devon) ; decussata (upper 

 green-s,and, Isle of Wight ; lower green-sand, Kent 

 and Sussex ; Blackdown) ; fibrosa (Blackdown, De- 

 von) ; forraosa (Blackdown) ; glabra (upper green- 

 sand, Isle of Wight; lower green-sand, Kent; 

 Blackdown, Devon); glabra? (lower green-sand, 

 Sussex) ; doubtful (upper green-sand, Hampshire ; 

 lower green-.sand, Kent) ; one or two other species 

 (lower green-sand, Sussex) ; new (lower green-sand, 

 Kent ; Oxford oolite, Cambridge) ; a Cucullar;a with- 

 out any designation (lower green-sand. North Wilts); 

 and a small species from the Portland sand, Dorset- 

 shire. 



" Mr. Lonsdale, in his elaborate paper ' On the 

 Oolitic District of Bath,' mentions CuciiUcdje ob- 

 longa (inferior oolite, Widcombellill) and Cucullaea 

 glabra (upper green-sand, neighbourhood ofWar- 

 min.ster). Mr. Murchison (' Silurian System') de- 

 scribes and figures CucuUaDa antiqua from the old 

 red-sandstone (middle and lower beds only) and the 



upper Ludlow rock ; Cue. Cawdori from the upper 

 Ludlow rock, with a ? ; and Cue. ovata from the old 

 red-sandstone (middle and lower beds only). Pro- 

 fessor Sedgwick and himself had previously given 

 Gosau as a locality for Cucullaea carinata. (' Struc- 

 ture of the Eastern Alps.') 



" Area. The number of fossil species (tertiary) 

 given by M. Deshayes in his Tables is iifty-lour, 

 several of which, as we have seen above, he records 

 as both living and fossil (tertiary). In the last edi- 

 tion of Lamarck no more tlian eighteen, fossil only, 

 are catalogued. Dr. Mantell mentions two or three 

 undetermined species from the chalk marl (Ring- 

 mer), and Area carinata from the firestone or upper 

 green-sand (Southbourn, Sussex, and Devizes) ; and 

 another (a very imperfect cast) from the gault or 

 Folkstone marl (Riugmer). Professor Phillijis notes 

 Arcoe quadrisulcata and aemula from the coralline 

 oolite, Yorkshire ; Mr. Lonsdale notes an Area from 

 the inferior oolite (canal banks opposite Limpley 

 Stoke), and another from Frome ; also one from the 

 Bradford clay. Professor Sedgwick and Mr. Mur- 

 chison record one from Gosau. Dr. Fitton gives 

 Area carinata from the upper green-sand, Hamp- 

 shire ; A. rotundata from Blackdown, and an uncer- 

 tain species from the lower green-sand, North Wilts, 

 the Portland stone, Oxford, and the Oxford oolite, 

 Cambridge. Mr. Murchison ('Silurian System') 

 describes and figures Area Eastnori from the Wen- 

 lock shale. 



" Pectuncnlus. Mr. G. B. Sowerby (' Genera') 

 states that all the species known to him are found 

 either in the London clay or the calcaire grossier ; 

 he says that a very neat one occurs in the indurated 

 marl at Bognor, where it is accompanied by fossil 

 Pinnae, Linguli, &c., and he has figured it, believing 

 it to be a variety of Lamarck's Pectunculus pulvi- 

 natus, ' but in truth,' he adds, ' it is so diificult to fix 

 the characters of the species of this genus, that we 

 dare not speak decidedly upon this point.' M. 

 Deshayes enumerates, in his Tables, twenty-seven 

 fossil species (tertiary), and of these he notices three, 

 as above mentioned, as both living and fossil (ter- 

 tiary). In the last edition of Lamarck but fifteen 

 species, fossil only, are catalogued. Dr. Mantell 

 notes Pectunculus pulvinatus flora the blue clay 

 of Bracklesham ; P. breviroslris and P. decussatus 

 from the arenaceous limestone or sandstone of Bog- 

 nor. Professor Sedgwick and Mr. Murchison enu- 

 merate Pectunculi Plumsteadiensis, ■ brevirostris, 

 pulvinatus? and calvus from the Gosau deposits: 

 and Mr. Lea describes and figures Pectunculi Bro- 

 deripii, minor, deltoideus, ellipsis, and obliqua from 

 the Claiborne beds (tertiary), Alabama. 



" Niicvla. The number of fossil species (tertiary) 

 published in the Tables of M. Deshayes is twenty- 

 three, and four are enumerated as both living and 

 fossil (tertiary). (See above.) In the last edition 

 of Lamarck only seven are catalogued as fossil only. 

 Dr. Mantell noticesNuculapectinatafrom the gault 

 or Folkstone marl ; and Nuc. impressa from Black- 

 down. Professor Phillips recoids Nuculae ovata 

 and subrecurva from the Speeton clay ; subrecurva 

 from the inferior oolite ; another from the coralline 

 oolite ; elliptica and nuda from the Oxford clay ; 

 variabilis and lachryma from the Bath and inferior 

 oolite ; axiniformis, inferior oolite ; ovum and com- 

 planata, upper lias; cuneata, tumida, undulata, ela- 

 viformis?, and Luciniformis (Bolland, &c.), and bre- 

 virostris, Harelaw, Northumberland. (Yorkshire.) 

 Mr. Lonsdale notes Nucula pectinata from the 

 Bradford clay ; and another from the ferest marble. 

 Professor Sedgwick and Mr. Murchison give us Nu- 

 culiB amygdaloides and concinna' in their list of 

 Gosau fossils. Dr. Fitton enumerates Nuculae an- 

 gulata (Blackdown) ; antiquata (lower green-sand, 

 Sussex, and Blackdown); apiculata (Blackdown); 

 bivirgata (gault, Kent) ; impressa (lower green- 

 sand, Sussex, and Blackdown) ; lineata (Blackdown); 

 obtusa (Blackdown) ; ovata (gault and lower green- 

 sand, Kent) ; pectinata (gault, Kent, Cambridge, 

 South Wilts, Blackdown, Devon) ; undulata? (gault, 

 Kent), and another (gault, Bedford). 



" Mr. Murchison figures and describes Nuculae ? 

 ovalis, and laevis ; the first from the upper Ludlow 

 rock, the second from the Llandeilo flags. (' Sil. 

 Syst.') Mr. Lea describes and figures Nuculae Sedg- 

 wickii, ovnla, pectuncularis, Brongniarti, media, 

 pulchcrrima, plieata, magna, carinifera, plana, and 

 semen, from the Claiborne beds." 



Family CHAMID^ (CLAMS, &c.). 

 Some naturalists of great eminence divide this 

 family into two, viz. Tridacnidae, of which the 

 great clam TridaenaGigasis the type, and Chamidae 

 represented by Chama and Dieeras. Certainly 

 these form two distinct sections, if with Cuvier 

 we include them under one family head. For the 

 Tridacna is furnished with a strong byssus as a mode 

 of attachment, and moreover has only one adductor 

 muscle, of great power, fixed in the middle of the 

 valves. It is an exception to the general rule, 

 being Monomyarian, 



