Zuoluyical Society. 357 



gitudinalibus elevatis jimbriato-decussatd ; ligamcnti ared antich 

 latiusculd, poslicr ucuminatd ; ligamento brcvi, ad posticam arete 

 partem solum adjiinclo. 

 Couch. Icon. Ana, pi. 16. f. 104. 



Hub. Mozambique Channel (found imbedded in madrcj)ore) ; 

 Hankey. 



The ligament and ligamentary area of this species present exactly 

 the same peculiar structure as those of the Area pusilla (Bj/ssoarea 

 pusilla, Sowerby, Proc. Zool. Soc. 1833) ; the shell is, however, alto- 

 gether larger, more acuminated posteriorly, and the sculpture is of 

 a smaller pattern. 



Arca tknebrica. Area testa oblongo-ovatd, lateribus angulato- 

 rotundatis ; fused, epidermide tenui indutd ; radiatim striatd, striis 

 elevatis, numerosis, confertis ; umbonibiis albidis, approximatis, 

 antice adjectis ; Ugamenti ared angvsid, postice lanceolato-acumi- 

 natd. 

 Conch. Icon. Arca, \A. 16. f. 10.5. 



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

 low water) ; Cuming. 



The umbones in this species are very anteriorly situated. 



Arca bullata. Arca testd ovato-quadratd, planiusculo-compressd, 

 lateribus svperm angulaiis, antico infra rotundato, postico angu- 

 lato-extenso ; fuscescente, epidermide tenui, subsetosd, setis in liris 

 longitudinalihus adjectis, indutd ; radiatim costatd, costis nodosis, 

 cosiis lateralibus grandibus, distant ibus, crenato -nodosis ; Ugainenti 

 ared angustd, elongatd, dcclivi. 

 Conch. Icon. Area, pi. IG. f. 107. 



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 epidermis being deposited only between the nodules. 



Arca volucris. Arca testd subquadratd, gibbosd, naviciilari, late- 

 ribus superne angulaiis, antico infra rotundato, postico angulato, 

 carind acutd ab umbone ad marginem decurrente ; albidd, fusco 

 sparsim tinctd ; striis elevatis longitiidinalibus et transversis decus- 

 satd, ared posticali costatd, costis latiusculis, crenatis ; nmbonibus 

 mucronatis, incurvatis ; Ugamenti ared latissimd, nigra unimacvlatd. 

 Conch. Icon. Arca, pi. IG. f. 109. 



Hab. Island of Burias, Philippines (found under stones at low 

 water) ; Cuming. 



This species belongs to that division of the genus of which the 

 Ai'ca NocE is the tj^pe, and is nearest aUied to the Arca imbricata. 



Arca ccelata. Arca testd ovato-quadratd, subcompressd , latere 

 antico brcvissimo, 7-otundato, postico angulato, margine ventrali 

 bgsso hiante ; alba; radiatim costatd, costis li7-is angustis elevatis 

 eleganter clathrutis, inter stitiis profundi excavatis, costis medianis 

 duplicatis, lateralibus confertim nodulosis ; nmbonibus antice ad- 

 jectis ; Ugamenti ared angustd, profundi declivi. 



