ARC A. 



species 



(Mus. Metcalfe.) 



Arca compacta. Arca testd subelongato-quadratd, in- 

 aquivalvi, gibbosd, lateribus supern't angulatis, antico 

 breviore, postico leviter angulato-extenso ; albidd, 

 epidermide fused partim indutd ; radial 

 costis t, , i tralis subaitgustis, planulatis, 



sinistralis latioribus, rotmidatis, iitterstitiin rancclla- 

 ti.-- ,- ligamenti area subangustd, declivi. 



The compact Auk. Shell rather elongately square, 

 inequivalve, gibbous, side- angulated al I 

 part, anterior side the shorter, posterior slightly 

 angularly extended ; whitish, partially covered with 

 a brown epidermis; radiately ribbed, ribs thirtj in 

 number, those of the right valve rather narrow, flat, 

 of the left valve wider, rounded, with the interstici - 

 cancellated ; area of the ligament rather narrow, 

 bent inwards. 



Pro. Zool, See.. 1844. 



Hab. ? 



This is a short compact shell of rather solid growth. 



U 



Species 28. (Mus. fuming.) 

 srtusa. Arca testd subobliqui quadratd, vix 



, lateribus superne angulatis, infra rotun- 



ila/i.-- ; iilliiihi, ririili'scentr I'm, In, rjiiilcn 



sparsim indutd , radiatim costatd, costis duabus vel 

 triginta, confertis, plano-convexis, subtilis- 

 sim'e pertnsis ; ligamenti ami latiusculd, umbonibus 

 subcentralibus . 



The pricked Ark. Shell rather obliquely square, nearly 

 equivalve. sidi s angulated at the upper part, rounded 

 beneath ; white, stained with lightgreen, sparingly 

 covered with a brown epidermis; radiately ribbed, 

 ribs two or three and thirty in number, close-set, 

 flatly convex, very finely pricked ; area of the liga- 

 ment rather wide, umbones nearly central. 



Reeve, Pro. Zool. Soc, 1844. 



Hab. Mouth of the Gambia, Africa. 



The ribs of this shell are very finely pricked or in- 

 dented, a character which I do not remember to have 

 observed in any other species. 



Species 29. (Mus. Cuming.) 



Arca cisti la. Arca testd subquadratd, inaquivalvi, la- 

 teribus supern't angulatis, antico infra rotundato, pos- 

 tico quadrato ; ulbd, qndn-midc trniii fuscescente, 

 costas squamosd, indutd; radiatim costatd, 



ws/i.i, nnnirriisis, srjitem vel OCtO el triginta, 



valva sinistralis umbones versus subtilissimi nodv- 

 losis ; ligamenti area mediocri; umbonibus subacutis, 

 prope extremitatcm anlicam di.yusith. 

 The little box Auk. Shell somewhat square, inequi- 

 valve, sides angulated at the upper part, anterior 

 :n ath, posterior square ; white, co- 

 vered with a thin, lighl brown epidermis, scaly be- 

 i ribbed, ribs narrow, im- 

 or eight and thirty in number, those 

 of the left valve very finely nodulous towards the 

 umbones . area i I the ligament middling; umbones 

 sharp, situated near the anterior extremity. 

 K i i \ i , Pro. Zool. Soc, 1 844. 

 Hab. ? 



An interesting species remarkable for the neatness 

 darity of the ribs, as well as for the very anterior 

 situation of the umbones. 



Species 30. (Mus. Cuming.) 



Arca intlata. Arca testd oblique ovatd, tenui, inflatd, 

 ivalvi, lateribus supernh leviter angulatis, in- 

 fra rolundatis ; albidd, epidermide corned fused, in- 

 ter costas squamosd, indutd; radiatim costatd, costis 

 numerosis, quadragenis, planulatis, Itevibus ; liga- 

 menti ared subangustd, declivi; umbonibus tumidis, 

 paululitm approximatis. 



The inflated Ark. Shell obliquely ovate, thin, in- 

 flated, nearly equivalve, sides slightly angulated at 

 the upper part, rounded beneath ; white, covered 

 with a brown horny epidermis, scaly in the inter- 

 stices between the ribs; radiately ribbed, ribs nu- 

 merous, forty in number, flat, smooth ; ligamentary 

 area rather narrow, bent inwards ; umbones swollen, 

 a little approximated. 



Reeve, Pro. Zool. Soc, 1844. 



Hab. Ilo Ilo, isle of Panay, Philippines (found in soft 

 mud at the depth of six fathoms) ; Cuming. 



February 1844. 



