ARC A. 



XVI. 



Species 



Af 



104. (Mus. Hankey.) 

 Donaciformis. Arca testd sub-Donaciformi, medio 



leviter coarclatd, latere antico brevissimo, truncato, 

 postico elongato, subacuminato ; albidd, epidermide 

 viz nulla, striis transversis et longitudinalibus ele- 



vulis fimlirinto-decussatd ; ligament! area antie'e la- 

 tinsi-ulii, postice acuminata; lir/ameuto brevi, ad pos- 

 ticam area partem solum adjunclo. 



The Donax-shaped Ark. Shell somewhat Donax- 

 shaped, slightly contracted in the middle, anterior 

 side very short, truncated, posterior elongated, 

 rather acuminated ; whitish, with scarcely any epi- 

 dermis, fimbriately decussated with raised trans- 

 verse and longitudinal stria; ; area of the ligament 

 rather broad anteriorly, acuminated posteriorly ; 

 ligament short, situated at the posterior portion of 

 the area only. 



Reeve, Pro. Zoo!. Soc, 1844. 



Hob. Mozambique Channel (found imbedded in madre- 

 pore) ; Hankey. 

 The ligament and ligamentary area of this species 



present exactly the same peculiar structure as those of 



the Area pusilla (PL XVIII.); the shell is, however, 



altogether larger, more acuminated posteriorly, and the 



sculpture is of a smaller pattern. 



Species 10.3. (Mus. Cuming.) 



Arca TENEBRICA. Area testa oblonejo-ovatd, later/bus 

 angulato-rotundatis ; fused, epidermide tenui indutd; 

 rai/iatim striata, striis eleeatis, numerosis, confertis; 

 umbonibus albidis, approximatis, antice adjectis ; liga- 

 menti area angustd, postice lanceolato-acuminatd. 



The dark Ark. Shell oblong-ovate, sides angularly 

 rounded ; brown, covered with a thin epidermis ; 

 radiately striated, stria; raised, numerous, close- 

 set ; umbones white, approximated, situated an- 

 teriorly ; area of the ligament narrow, lanceolately 

 acuminated posteriorly. 



Reeve, Pro. Zool. Soc, 1844. 



Hab. Basey, island of Samar, Philippines (found under 

 stones at low water) ; Cuming. 



The umbones in this species are very anteriorly situ- 

 ated. 



Species 106. (Mus. Cuming.) 

 Arca solida. Arca testa' ovato-quadrntd, sulidijuilaterali, 

 rrassii, soli/hi, gibbosissimd, lateribus rotunda/is, 

 postico obtuse angulato, obsolete carinato • albidd, 



epidermide vix nulld ; radiatim striata, striis elevatis, 

 striis longitudinalibus minutis subindistincfe et irre- 



fjtilurilcr caneellatis ; umbonibus centratibus : liga- 

 ment i area elanrjatd , subdeetiri ; ligament o rhomboideo, 

 central!. 

 The solid Ark. Shell ovately square, nearly equila- 

 teral, thick, solid, very gibbous, sides rounded, the 

 posterior obtusely anguhited, obsolete]}' keeled ; 

 whitish, with scarcely any epidermis; radiately 

 striated, stria 1 elevated, rather indistinctly and irre- 

 gularly cancellated with minute longitudinal stria- ; 

 umbones central , area of the ligament elongated, 

 somewhat bent inwards; ligament diamond-shaped, 

 central. 



Byssoarca solida, Sowerby, Pro. Zool. Soc, 1844. 

 Hab. Payta, coast of Peru (found under stones) ; Cu- 

 ming. 

 This species may be recognised by its extremely gib- 

 bous growth. 



Species 1(17. (Mus. Cuming.) 

 Arca bullata. Arca testa ovato-quadratd, planiusculo- 

 compressd, lateribus superne angulatis, antico infra 

 rotundato, postico angulato-extenso ; fuscescente, epi- 

 dermide tenui, subsetosd, setis in liris longitudinalibus 

 adjectis, indutd ■ radiatim eastatd, costis nodosis, costis 

 lateralibus grandi/ais, distaiitibus, crenato-nodosis , 

 ligament i area angustd, elongatd, declivi. 

 The studded Ark. Shell ovately square, rather flatly 

 compressed, sides angulated at the upper part, an- 

 terior rounded beneath, posterior angularly ex- 

 tended ; light brown, covered with a thin, rather 

 bristly epidermis, bristles lying in longitudinal 

 ridges ; radiately ribbed, ribs nodulous, side ribs 

 large, distant, crenately noduled ; area of the liga- 

 ment narrow, elongated, bent inwards. 

 Reeve, Pro. Zool. Soc, 1*44. 



Hab. ? 



The nodules of the radiating ribs are arranged in 

 longitudinal rows with so much regularity, that the 

 shell has all the appearance of being cancellated, the 

 effect of which is increased by the bristles of the epi- 

 dermis being deposited only between the nodules. 



Species 108. (Mus. Cuming.) 



Arca divaricata. Arca testa ovato-ublongd, latere 



antico superne subangulato, postico rotundato, sub- 



concavo-compresso, carind ab umbone ad marginem 



deeur rente ; albd, epidermide v'uc nulld ; longitudi- 



May 1844. 



