A \i C A, 



Plate VI. 



Species 34. (iMus. Cuming.) 

 Aiu \ concinna. Arcatestd elongato-ovatd, subcylindra- 



ced, inaequivalvi, lateribus supem? anyuhtis, infra ro- 

 tundatis; albidd, epidermide tenui fuseeso 



ctislim rjHissimi sftusti. inilutd ; rudiutim costatd, 

 costis ad tricenas, anterioribus ruyu/asis.sulra diri.-is. 

 interstitiis lineis elrvatis di-iiissu/i.< ; liyamenti art a 

 angustd, elongatd, antic't utrinque crenulatd. 

 The elegant Ark. Shell elongately oval, somewhat 

 cylindrical, inequivalve, sides angulated at the upper 

 part, rounded beneath ; whitish, covered with a 

 very thin light brown epidermis, very finely bristly 

 between the ribs ; radiately ribbed, ribs about thirty 

 in number, the most anterior ones wrinkled and 

 divided by a groove, interstices between the ribs 

 crossed with raised lines; ligamentary area narrow, 

 elongated, crenulated at the anterior end on both 

 sides. 

 Soweebt, Pro. Zool. Soc., 1833. 

 Hab. Gulf of Nicoiya, Central America (found in 



sand at the depth of twelve fathoms) ; Cuming. 

 .Mr. Sowerby describes this shell as having ligament 

 on the posterior side only : this, however, is impossible; 

 the ligament was rubbed off the anterior side of the spe- 

 cimen which served for his description. 



Species 35. (Mus. Brit.) 



Abca auriculata. Area testd ovato-cordald, cequivalvi, 

 lateribus supern't angulatis, antico brevissimo, postico 

 subcompresso, plus minusve auriculata : albidd, epi- 

 dermide olivaceo-f used indutd ; radiatim costatd, cos- 

 tis <id tricenas, noduloso-crenatis ; liyamenti ana 

 elonyatd, subangustd. 



The adriculated Auk. Shell ovately heart-shaped, 

 equivalve, sides angulated at the upper part, ante- 

 rior side very short, posterior somewhat compressed, 

 more or less auriculated ; whitish, covered with an 

 olive-brown epidermis ; radiately ribbed, ribs about 

 thirty in number, nodulously crer.ated ; area of the 

 ligament long and rather narrow. 



Lamarck, Anim. sans vert. (Deshayes' edit.), vol. vi. 

 p. 47-2. 



Chen-u, Delessert's Recueil de Coquilles, pi. 11. f. 12. 

 a, b, c, 



Hab. ? 



Care must be taken not to confound this shell with 

 the young of Area Deshayesii, which is also auriculated, 

 but of more slender growth. 



Spi cies 36. (Mus. Cuming.) 

 Am \ Gambiensis. Area testd elongato-quadratd, tenui- 

 cnla, valih compressd, in media coarctatd, aquivalvi, 

 lateribus rotundatis, postico subangulato extenso ; al- 

 bidd, epidermide tenui olivaced, sparsim setigerd, in- 

 dutd; radiatim costatd, costis duabus vel tribus it 

 riyinti, lawigatis, plano-expansis, lird exili intercur- 

 rente; liyamenti area parvd, angustd ; umbonibus an- 

 gulato-mucronatis. 

 The Gambia Auk. Shell elongately square, rather 

 thin, very compressed, contracted in the middle, 

 equivalve, sides rounded, posterior rather angularly 

 extended; whitish, covered with a thin olivaceous 

 epidermis, armed here and there with fine bristles ; 

 radiately ribbed, ribs two or three and twenty in 

 number, smooth, flatly expanded, with a fine ridge 

 running between them ; area of the ligament small, 

 narrow ; umboncs angularly pointed. 



Pro. Zool. S«,c., 1844. 

 Ilah. Mouth of the Gambia, Africa (found in sandy mud 

 in dee]) water). 



The ribs of this shell become peculiarly flattened and 

 spread oui towards the margin, and there is a fine ridge 

 running down the centre of the intermediate grooves. 

 Thi> is the only species in which I have as yet observed 

 any kind of fine interribbing. 



Species 37. (.Mus. Cuming.) 

 AftCA CDNEATA. Aria testa obliqu'l ariitd, teijiiiia/ri, 



marginem versus coarctatd, lateribus superne angu- 

 latis, infra oblique rotundatis; albidd, radiatim cos- 

 tatd, costis ad vicenas, rotundatis, irregulariter no- 

 dosis; liyamenti area latissimd, declivi ; umbonibus 

 parvis, distantibus. 

 The wedge-like Auk. Shell obliquely ovate, equivalve, 

 contracted towards the margin, sides angulated at 

 the upper part, obliquely rounded beneath ; whitish, 

 radiately ribbed, ribs about twenty in number, 

 rounded, irregularly noduled ; area of the ligament 

 very wide, bent inwards ; umbones small, distant. 



February 1844. 



