Cockles.] 



MUSEUM OF ANIMATED NATURE. 



275 



surrounded by papillae, one (the more central ol* the 

 two) for respiration. 



The number of livinp; species is very limited, M. 

 Deshayes enumerating only eight as living and fossil 

 (last edit, of Lamarck). 



The recent species are found in the European 

 seas, and those of India and Australia. 



2955, 2956. — The Heart Isocardia 



i^Isocardia Cor). Chama Cor, Linn. Referrina; 

 to Fig. 2355, A represents the animal as it appears 

 between the partially opened valves; the two 

 ciliated siphons are visible, the edges of the 

 mantle, and a portion of the foot ; B shows the 

 animal in one of the valves : the large sharp-edged 

 foot, and the two muscular surfaces, are well seen ; 

 the mantle is cut away to a great extent. Fig. 29.56 

 shows the beautiful shell of Isocardia Cor with the 

 valves closed. 



This species is a native of the Mediterranean and 

 ^ other seas of Europe. In the ' Zool. Journal,' vol. 

 ii. p. 359, will be found some observations on 

 the present mollusk by the Rev. James Bulwer, 

 vrho studied the habits of the species from some 

 specimens trawled up in deep water on the east 

 coast of Ireland. These he put into a vessel of sea- 

 water for examination. The shell opened, as at A, 

 Fig. 2955, and the feelers or cilia of the anterior 

 siphon (the respiratory siphon), the largest of the 

 two, moved slowly as if in search of food. Having 

 remained in this situation about ten minutes, water 

 was ejected with considerable force from the 

 posterior orifice, which had till then remained 

 motionless. The expulsion of the water appeared 

 to be effected by a sudden contraction of the 

 muscles, because this was never done without the 

 valves nearly closing at the same instant. After a 

 few seco:ids the valves gradually returned to their 

 open position, and remained quiescent as before, 

 till the water was again ejected with a jerk. This 

 alternating process was repeated during the whole 

 time his specimens were under examination, but at 

 shorter intervals on receiving fresh supplies of sea- 

 water. The animal appeared to Mr. Bnlwer to be 

 insensible both to sound and light ; its sense of 

 feeling, on the contrary, appeared to be exquisitely 

 susceptible ; minute substances dropped into the 

 orifice of the mantle instantly excited the animal, 

 and a column of water, strongly thrown out, expelled 

 them from the shell. With so much force was the 

 water in some instances ejected, that it rose above 

 the surface of three inches of superincumbent fluid. 

 Its movements, ever, howwere interrupted neither 

 by the presence or absence of light, nor by noises 

 however loud. 



Leaving Isocardia within the pale of the Chamidae, 

 we pass to another and extensive group. 



Family CARDIID.E (COCKLE, MACTRA, &c.). 



Cuvier institutes a great section, or, as he terms it, 

 family, of the acephalous bi-valve mollusks, to which 

 he gives the title of Les Cardiaces, equivalent to 

 the family Conchacea of M. de Blainville. Of this 

 section Cuvier gives the following general charac- 

 teristics : " In all the mantle is open anteriorly, but 

 posteriorly it presents two siphons or orifices, one 

 lor respiration, the other for the egesta. These form 

 tubes sometimes distinct, sometimes united into a 

 single mass. There is always a transverse adductor 

 mu-icle at each extremity of the shell, and a foot 

 which generally serves for the purpose of locomo- 

 tion. It may be laid down as a rule, that the 

 species with elongated siphons live buried in the 

 mud or sand. This condition of organization may 

 be recognised on the shell, by the more or less 

 developed contour which the impression of attach- 

 ment of the borders of the mantle describes, before 

 uniting with the impression of the posterior 

 transverse muscle." The Conchacea of De Blainville 

 are equivalent to the oriler Phyllopoda of Mr. Grey, 

 which he divides into the families Veneridae, Cyre- 

 nidae, and Cardiidae. 



Of these families, instituted by Mr. Grey, referring 

 them as subfamilies to the Cardiidae, or Conchacea, 

 we shall select a few prominent examples. 



The first genus to be noticed is Cardlum, of which 

 the well known cockle (Cardium edule), la Coque 

 or Sourdon of the French, is known to all. The 

 cockles, like many other bi-valves, have an equivalve 

 shell, subglobular and cordiform, with umbones 

 convoluted towards the hinge ; the hinge is formed 

 by four teeth in each valve, two cardinal and 

 oblique, two lateral and distant ; the valves have 

 radiated ribs and toothed borders. 



The animal is furnished with a very large cylin- 

 drical foot, bent elbow-like about the middle, 

 directed forwards, and terminating subconically ; 

 the lobes of the mantle, bordered interiorly by ten- 

 tacular papillae, are united posteriorly with two very 

 short siphons or mere apertures, ciliated around the 

 margin ; mouth transverse with small appendages. 

 These shells are very widely distribulcd, the seas of 

 Vol. II. 



almost every warm and temperate climate abound 

 with them, and one species at least (Cardium ra- 

 diatum), brought home by Captain Parry, is a native 

 of the Polar Ocean. In the ■ Proceeds. Zool. Sue' 

 1833, will be found descriptions of fourteen new 

 species, by Mr. \V. B. Soweiby, and of one by Mr. 

 Broderip ; they were brought home by Mr. Cuming 

 from the western coast of South America and the 

 islands of the South Pacific Ocean. 



The cockle tribe generally live on sandy shores, 

 at a depth varying from the surface to thirteen 

 fathoms. They bore into the sand by means of 

 their powerful foot, which enables them also to leap 

 with considerable vigour. Many species attain to a 

 considerable size. 



Fig. 29.57 shows the characters of the valves and 

 hinge of Cardium elongatum. 



From the genus Cardium may be separated into a 

 subgenus, under the name of Hemicardium, such 

 species as have the valves compressed from before 

 backwards, and strongly keeled down the middle. 

 It would be strange, says Cuvier, if the animal did 

 not present some modification in accordance wiih 

 this singular configuration. M. Rang corroborates 

 Cuvier's observation, from the examination of living 

 individuals of Cardium (Hemicardium) Cardissa. 

 M. Deshayes, however, considers that the form can 

 only be admitted as a section. 



Fig. 295S represents the Cardium (Hemicardium) 

 Cardissa, of the natural size ; a spotted variety. 



Of the living species of the Cardium about fifty 

 are known, and between thirty and forty of fossil 

 species ; the latter occur in most of the fossiliferous 

 strata, from the cretaceous to the grauwacke group, 

 and appear to be most abundant in the crag, the 

 London clay, the greensand, and the contempora- 

 neous beds. 



We next turn to the genus Capsa. In this genus 

 the shell is transverse, equivalve, inequilateral, and 

 not gaping ; the cardinal teeth diverge from a point 

 close to the umbo ; in one valve there are no lateral 

 teeth, in the other one distinct cardinal tooth, and 

 two distant, very obsolete, lateral ones ; ligament 

 external ; a large sinus in the pallial impressions. 



The animal has the mantle considerably open at 

 its marginal border for the passage of a very com- 

 pressed and large foot; the siphons are separated 

 and of considerable length, wiih tentacular papillae 

 at their orifices. 



The shells of this genus are natives of the warm 

 and temperate seas ; they lie buried at a small 

 depth in the sandy mud, with the posterior part 

 upwards to facilitate the influx of water for respira- 

 tion. The depth at which they are found varies 

 from five to twelve fathoms from the surface of the 

 water. 



2959. — The Bbazilian Capsa 



(Capsa Brasiliensis). Of the genus Capsa M. 

 Deshayes only records two species, viz. the Brazilian 

 Capsa and the Capsa laevigata ; and he considers 

 that the genus should be suppressed and referred to 

 Donax. In the ' Proceeds. Zool. Soc' 1832, a species 

 from Peru and Central America is described by Mr. 

 G. B. Sowerby, under the title of Capsa altior. The 

 inside of the valve of Capsa Brasiliensis shows the 

 two muscular impressions, and the form of the 

 pallial impressions, as well as the characters of the 

 hinge. 



With respect to the genus Donax, these shells 

 have the hinge nearly as in Cardium, but their shell 

 is of a different form, being triangular, with the 

 obtuse point at the umbones of the valves and the base 

 of the triangle at their margin ; the shortest side is 

 that which presents the ligament, viz., the posterior 

 part of the shell, a circumsl[ance rare among bivalves, 

 which have in general the posterior part of the shell 

 the longest. It may, however, be repeated that 

 many call the portion of the shell which has the 

 ligament the anterior, and the part which presents 

 the lunule the posterior, of the shell, reversing the 

 valves entirely: and accordingly Mr. G. B. Sowerby 

 says, " Lamarck is at issue with himself when he 

 calls the ligament posterior in Donax ; for the sake 

 of consistency we must continue to call the side on 

 which the ligament is placed, as well as the sinus on 

 the muscular impression on the mantle, whether it 

 be the shorter or longer, the anterior side. We are 

 aware that Cuvier has pointed out the impropriety 

 of this; but the term anterior is generally adopted 

 for the side (end) which bears the ligament, and the 

 posterior for the opposite side (end)." 



M. Deshayes, in his edition of Lamarck, well 

 observes that the terms anterior and posterior, as 

 used by that zoologist, are badly applied, and that 

 it must not be concluded, as some have done, that 

 the Donaces and Tellinae have the ligament on 

 the anterior side. Adanson, he remarks, has doubt- 

 less assisted in confirming the error that the former 

 have the ligament placed on the anterior side ; for, 

 probably through inadvertence, in rei)resenting the 

 animal of Donax, he makes the foot protrude from 



the short end, which bears the ligament, and the 

 siphon from the long end of the shell, thus reversino' 

 the animal in the valves. The fact is that in Donax" 

 I as in the rest of the Conchifera, the anterior and 

 posterior part of the shell, and the left and right 

 valves, may be determined by placing the shellon 

 edge, with the ligament posteriorly ; this will make 

 the long acute end in Donax the anterior (whereas 

 in most the lunular or anterior end is the shortest), 

 and the end whence the siphons are protruded, viz. 

 the posterior, the shortest. 



In general the Donaces are small shells prettily 

 striated ; the umbones are but little prominent, and 

 nearly vertical ; the foot is compressed and angular, 

 ■and there are two siphons, capable of being retracted 

 into a sinus of the mantle. 



The genus is widely extended, species existing in 

 all seas. Several are natives of the European 

 coasts. They lie buried in sand and sandy mud, 

 with the posterior, or (in them) the short end, of the 

 shell uppermost, for facilitating the entrance of 

 water through the respiratory siphon. 



Fig. 20GO represents the hinge and inside of the 

 valves of Donax Scortum. The fossil species of 

 this genus are not very numerous. They are said 

 to occur principally in blue marls in the South of 

 France, and in the oolitic series. 



The genus Gratelupia, on the contrary, occurs 

 only in a fossil state. Two species are recorded, 

 one, the Gratelupia donaciformis, from the marine 

 tertiary beds of Merignac, the other, G. Moulinsii, 

 from Claiborne, Alabama (America), in tertiary 

 strata of the same period, according to Mr. Lea, as 

 the London clay and the calcaire grossier of Paris. 



Figs. 2961 and 2962 represent the Gratelupia 

 Moulinsii, and convey a clear idea of the characters 

 of the genus. 



Our next genus for inspection is Tellina, which in 

 some respects agrees with Donax. The shell is 

 elongated and compressed, regular and sometimes 

 slightly inequilateral : the anterior side is sometimes, 

 but not always, longer than the posterior, which 

 latter is often angular with a flexuous and irregular 

 bend at its lower border ; the umbones are small ; 

 the hinge presents three cardinal teeth, and two 

 lateral ones, which are often distant, with a hollow 

 at their base in each valve. 



In the mollusk the tubes are very much elongated 

 and separated, and capable of being withdrawn into 

 a fold of the mantle. 



The genus Tellina is widely spread, but is most 

 abundant in the warmer seas. Like the Donaces, 

 these shells bury themselves in the mud, and in beds 

 of sand, often at the depth of sixteen or seventeen 

 fathoms. The species are very numerous, upwards 

 of sixty being described. 



Fig. 2963 represents the Tellina rostrafa, which 

 may be regarded as a fair example of the genus. 



From the genus Tellina M. Lamarck separated 

 such species as are rather rounded or oblong in 

 contour, the valves presenting no decided flexuous 

 bend, the hinge having two divergent cardinal teeth, 

 and two distant lateral ones, of which the anterior 

 is but little distant from the umbo. For these 

 species he founded the genus Tellinides. 



This genus is admitted by Mr. G. B. Sowerby, 

 but not by MM. Rang, De Blainville, or Deshayes. 

 It may be retained, however, if only for the sake of 

 convenience. Mr. Sowerby observes that the 

 number of shells which may be ranged under it is 

 rather considerable, although Lamarck has only 

 mentioned one. The species referable to Tellinides 

 inhabit the same sea and display the same burrow- 

 ing habits as those of Tellina. 



Fig. 2964 represents the inside of one of the valves 

 of Tellinides. 



Of these two genera, granting this rank to Telli- 

 nides, there are not many fossil species. Deshayes, 

 in his last edition of Lamarck, gives only sixteen, 

 though previously in his table he had enumerated 

 fifty-four. Four fossil species are to be added, 

 which were collected by Mr. James Bnrton from 

 the western borders of the Red Sea. 



Another genus founded by Lamarck is Amphi- 

 desma, which M. Deshayes remarks is not very 

 natural, but may be retained till it has undergone 

 the necessary scrutiny and reform. 



The shell issuboval, of little thickness, inequila- 

 teral, sometimes a little gaping ; the hinge presents 

 one or two cardinal teeth, and sometimes lateral 

 teeth. Lig.ament double ; one portion external, the 

 other internal. 



The genus is widely spread, occurring in the 

 European seas (English Channel, Mediterranean, 

 &c.), those of South America, New Holland, &c. ; 

 They are found in sands and mud, sometimes as 

 deep from the surface as forty fathoms. Lamarck 

 enumerates sixteen species; to these must be 

 added twelve new ones described by Mr. Sowerby 

 in the * Proceeds. Zool. Soc' for 18:32, from specimens 

 brought by Mr. Cuming from the western coast of 

 South America and the islands in the South Pacitic 

 Ocean. 



2 N2 



