:?d 



March 12. 1844. 

 William Yarrell, Esq., Vice-President, in the Chair. 



Mr. Loveli Reeve described thirty-three new species of Arca : — 



Arca pilula. Arca testd orbiculari, valde gibbosd, subinteguivalvi, 

 vicc inteijui/aierali, lateribus superne angulatis, infrci rotundatis ; 

 albidd, fuscescente pallide tinctd, epidermide fuscd, inter costas 

 setosd, indutd ; radialini costatd, costis quinque vel $ex et viginti, 

 angustis, valv<e sinistralis omnibus, valvce dextralis anticis tantum, 

 subtUiter tiodulosis; umbonibtts subremotis, ligamenti ared elongato- 

 rhomboided. 



Conch. Icon. Arca, pi. 2. f. 8. 



Hab. Island of Buriąs, Philippines (found in sandy mud at the 

 depth of six fathoms) ; Cuming. 



This species is so exceedingly gibbous that the shell is as wide as 

 it is high, and it is the šame in aU stages and varieties of growth. 



Arca anomala. Arca testd giiadrato-ovatd, subcoinpressd, in<Equi- 

 valvi, latere antico rotundato, postico subangulato-rotundato ; albd, 

 viridescente pallide tinctd, epidermide corned inter costas sparsim 

 indutd į radiatim costatd, costis octo et viginti, valva destralis 

 IčEvibus, planulatis, sinistralis convexis, nodulosis ; ligamenti ared 

 angustd. 

 Conch. Icon. Arca, pi. 2. f. 9. 



Hab. ? 



It seems rather anomalous that the ribs in one valve of this sheU 

 should be convex and nodulous, vvhilst in the other they are flat and 

 smooth ; but it is an interesting fact that the larger valve of the in- 

 equivalve species of Arca exhibits a much more elaborate style of 

 sculpture than the smaller. The Arca pilula just described shows 

 this remarkable peculiarity very distinctly, but not so prominently 

 as the species under consideration ; and it now remains to be deter- 

 mined whether this difference arises from any superiority of organi- 

 zation in the left lobe of the mantle of the animal inhabitant. 



Arca holoserica. Arca testd obliąue ąuadratd, tequivalvi, lateribus 

 superne angulatis, antico infra rotundato, postico angulato-extenso ; 

 albidd, epidermide holoserica obtectd ; radiatim costatd, costis 

 duabus vel tribus et triginta, creberrimis, planulatis, umbones ver- 

 sus yninutissime pertuso-cancellatis ; umbonibus subobliquis ; liga- 

 menti ared latiusculd. 



Conch. Icon. Arca, pi. 2. f. 11. 



Hab. Island of Samar, Philippines (found in coarse sand and gra- 

 vel at the depth of four fathoms) ; Cuming. 



This is a very fine species, remarkable not only on account of its 

 Nos. CXXXIII. & CXXXIV.— Proceedings of the Zool. Soc. 



