358 Zoological Society. 



Conch. Icon. Area, pi. 16. f. 110. 



Hab. } 



The sculpture of this shell is of the most exquisite description, 

 and reminds one forcibly of the delicate embossed carving of the 

 Chinese. 



Arca cometa. Area testd elongatd, latere antieo brevissimo , at- 

 tenuato, rotundato, postieo longissimo, plano-angulato ; albidd ; 

 radiatim striatd, striis elevatis, posticis latioribus, prominentibus, 

 dislantioribus, subsquamosis ; umbonibus antice adjeetis ; ligamenti 

 ared angustd. 



Conch. Icon. Arca, pi. 16. f. 111. 



Hab. Sorsogon, island of Luzon, Philippines ; Cuming. 



The posterior striae acquire almost the importance of ribs. 



Arca olivacea. Area testd ovato-quadratd, tenuiculd, subagui- 

 laterali, lateribus rotundatis ; albidd, epidermide olivaceo-fused 

 tenui corned indutd ; subtilissime radiatim striatd, striis numerosis, 

 confertis ; ligamenti ared mediocri, umbonibus subcentralibus . 

 Conch. Icon. Area, pi. 16. f. 113. 



Hab. San Nicolas, island of Zebu (found in sandy mud at the depth 

 of four fathoms) ; Cuming. 



This shell is not much unlike the Arca lactea in general appear- 

 ance ; it will be found, however, on examination to be a much thinner 

 and more delicate shell, whilst the umbones are sharper and more 

 closely approximated. 



Arca minuta. Arca testd orbiculari-ovatd, subcequivalvi, lateribus 

 superne angulatis, infra rotundatis ; albidd, subpellucidd, epider- 

 mide tenui main indutd ; radiatim striatd ; ligamenti ared latius- 

 culd, ligamento parvo, centrali. 

 Conch. Icon. Arca, pi. 17. f. 112. 



Hab. Philippine Islands (found in coarse sand at the depth of six 

 fathoms) ; Cuming. 



A very minute species, which cannot be referred to any hitherto 

 described. 



Arca navicella. Arca testd quadrato- elongatd, subcompressd, 

 lateribus superne angulatis, antieo infra rotundato, postieo angu- 

 lato, carina ab umbone ad marginem decurrente ; radiatim striatd ; 

 albidd, fusco postice sparsim strigatd ; ligamenti ared elongatd. 



Conch. Icon. Arca, jdI. 17. f. 114. 



Hab. Calapan, island of Mindoro, Philippines (found in coarse sand 

 at the depth of ten fathoms) ; Cuming. 



This is a little species of the Arca Note or naviform group. 



Arca lateralis. Arca testd oblique trapeziformi, lateribus superne 

 angulatis, antieo brevissimo, postieo latissimo, oblique expanse; 

 radiatim costatd, costis numerosis, angustis, crenatis, epidermide 

 subpilosd indutd ; ligamenti ared parvd. 



Conch. Icon. Area, pi. 17. f. 115. 



Hab. Philippine Islands ; Cuming. 



The peculiarly oblique growth of this species renders it extremely 



