401 



POLYODOSTA. 



POLYODONTA. 



432 



generally thick, regular, equivalve, inequilateral, with a similar hinge 

 in each valve always formed of serial teeth, which are often lamellar, 

 fitting iuto each other, straight or oblique ; muscular impressions 

 nearly always united by a paUial impression, which is very narrow, 

 and parallel to the border of the shell. 



Cuculltea (Lam.). Animal very thick, having the mantle a little 

 prolonged backwards, and bordered by au irregular row of tentacular 

 filaments ; labial appendages small and triangular ; foot large, pedun- 

 culated, compressed, and slit longitudinally. Shell thick, navicular, 

 equivalve, inequilateral, ventricose, with distant umbones; hinge 

 linear, straight, formed of small transverse teeth for the greatest part 

 of its length, and of many other teeth or longitudinal ribs ; ligament 

 entirely external ; anterior muscular impression forming a projection 

 with an angular or auriculate border. (Rang.) 



There is only one recent species of Cucullcea. 



This species is the Area concamei-ata of Martini, A. OucuUtu of 

 Gmelin, A. cucullata of Chemnitz, and Cucullcea anriculifera of 

 Lamarck, under which last name it is generally known; but, as M. 

 Deshayea well remarks, Martini's name has the priority, and it ought 

 to be that by which the species should be designated. 



The shape of the shell, which is of fair size, will be seen better from 

 the subjoined cut than from verbal description. The longitudinal 

 striae are more marked than the transverse stria;. The colour is rather 

 a deep cinnamon-brown externally, and internally on the anterior 

 part brown tinged with violet. It is a native of the Indian Ocean ; 

 eandy bottoms. 



Oiicullira auriculifera. 



There arc about 100 species of Cucullcea fossil, chiefly Silurian. 



Area (Linn.). Animal more or less thick, generally rather elon- 

 gated ; mantle prolonging itself slightly backwards, and with a row 

 of tentacular filaments on its borders ; labial appendages very small 

 and slender; foot pedunculated, compressed, and slit throughout its 

 length. 



Shell navicular, rather thick, equivalve, inequilateral, elongated, more 

 or less oblique ; umbones distant and often a little recurved forwards ; 

 hinge linear, straight, furnished throughout its length with a numerous 

 row of small teeth or transverse lamina;, which are equal and intrant ; 

 ligament entirely external. 



M. Rang, who gives the above as the characters of A rca, remarks that 

 the species sometimes adhere by their foot, and more frequently by 

 means of a byssus. 



M. De Blainville divides the Arete into the following subdivisions : 



A. (Le., Navicules). Navicular species; the hinge completely straight; 

 the foot tendinous and adherent. (Bijtioarea, Sw.) [BrssOABCA.] Ex. 

 Area Ntxe. 



B. (Les Bistourndes ; Genus Tritii, Oken.) Ex. A. torluosa. 



C'. (Genus Cucullaa, Lam.) Navicular species ; the hinge completely 

 rtraight; the terminal teeth much longer and more oblique than the 

 others. Ex. C'ueulltca auriculifera, Lam. 



HAT. HIST. DIV. VOt. IV. 



D. Species with a straight hinge not notched or not gaping iuferiorly. 

 Ex. A. barbata. 



E. (Les Rhomboides.) Species well closed, of less elongated form, 

 more pectinoid, and with a straight hinge. Ex. A. rhombea. 



F. Oval species, elongated or a little arched longitudinally, slightly 

 gaping inferiorly, with the umbones at a little distance from each 

 other, the ligament nearly internal, and the dental line a little bent. 

 Ex. A. mytiloidea. 



The number of recent species recorded by M. Deshayes, in his 

 Tables, is 43. Woodward gives 130 species. 



The following descriptions and cuts will give some idea of the dif- 

 ference of form assumed by the shells of this genus : 



A. Note. Shell oblong, striated; apex emarginate; umbones very 

 remote, incurved; margin gaping. It inhabits the Atlantic Ocean and 

 seas of Europe. 



Area Noa. 



a, valves closed, with the umbones and area of the binge towards the spec, 

 tator j t, valves closed, with the ventral or inferior aspect, showing the margin, 

 opposite to the spectator ; c, internal view of one of the valves. 



A. tortuota (Genus Trisii, Oken). Shell twisted, parallelepiped, 

 striated : valves obliquely carinated; umbones small, recurved. It 

 inhabits the Indian Ocean. 



A. antiquata. Shell transverse, obliquely cordate, ventricose, many- 

 ribbed ; tho ribs transversely striated and blunt ; the posterior ribs 

 bifid. Colour white. 



Lamarck gives the Indian Ocean, tha coasts of Africa, and the 

 Mediterranean, as the localities of this species, of which M. Deshayes. 

 in the last edition of the ' Animaux sans Vertebres,' says that he is 

 convinced that since the time of Liumcus two species at least have 

 been confounded under the denomination of A. antiquata, although 

 they are easily distinguished ; the one, more transverse, has the car- 

 dinal surface always furrowed into lozenge shapes when the valves are 

 united ; the other having a thicker shell, the ribs flatter, wider, and 

 striated, but never with furrows on the cardinal surface. This last, 

 being the most common and most anciently known, should, in his 

 opinion, retain the name of A. antiquata, and he cites the following 

 figures of the shell : ' Gualt. Test.,' pi. 87, f. C. ; Chemn., ' Conch.,' 

 t. vii. pi, 55, f. 548 ; ' Encyclop.,' pi. 306, f. 2 ; Qronov., ' Zooph.,' 

 pi. 18, f. 13. M. Deshayes further remarks, that the shell figured by 

 Poli and cited by Lamarck in the synonymy constitutes a species dis- 

 tinct from the two others. He adds that this, which inhabits the 

 Mediterranean, is the living analogue of A. diluvii. Neither, in his 

 opinion, is the A. antiquata of Brocchi a true A. antiquata, but the 

 A. diluvii, the fossil analogue of the species figured by Poli. 



The Arete have hitherto been found on bottoms of sandy mud and 

 dirt, at depths varying from the surface to seventeen fathoms. Some 

 of the species are moored to stones, corals, &c. 



2o 



