124 



elevatis ; umbonibus depressiusculis, approximatis ; ligamenti ared 

 parvd, angustd, profunde declivi. 

 Conch. Icon. Arca, pi. 12. f. 77. 



Hab. Coast of Japan (found under stones) ; Dr. Siebald. 

 Very likę a Modiola in shape, but not the recent analogue of the 

 fossil A. Modiolaformis of Deshayes. 



Arca cunealis. Arca testd elongatO'Oblongd, lateribus superri^ 

 angulatis, antico brevi, rotundato, postico eJongato, ungulato, carind 

 ab unibone ad marginėm deciirrente, margine ventrali by^so Mante ; 

 pallidefiiscd, epidermide molli lamellatd indiiftd ; radiatim striatd, 

 striis elevatis, fortiter granulosis, ared posticd subindistincti nigri- 

 costatd; umbonibus siibapproximatis , ligamenti ared latiusculd, 

 concavd, suleis Ugamentariis anticis posticiscue, subdistantibus. 

 Conch. Icon. Arca, pi. 13. f. 87. 



Hab. Zanzibar (found under stones at low water) ; Thorn. 

 The sculpture of this species corresponds precisely to that of the 

 Arca mutabilis ; the form of the shell is more depressly elongated, the 

 anterior side is shorter, and there are ligamentary grooves on the 

 posterior part of the cardinal area as well as on the anterior. 



Arca tenella. Arca testd subcylindraceo-oblongd, Modiolteformi, 

 tenui, siibpellucidd, lateribus obtuso-rotundatis, margine ventrali 

 vix hiante ; pallide fuscescente, epidermide molli leviter indutd ; 

 radiatim subtilissime striatd, striis granulosis ; umbonibus obtusis, 

 antice incurvis ; ligamenti ared antice latiusculd, postici lanceolato- 

 acuminatd. 

 Conch. Icon. Arca, pi. 14. f. 91. 



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

 water) ; Cuming. 



A delicate light bro\vn shell, beautifuUy striated, ■vvith a soft scat- 

 tered epidermis. 



Arca setigera. Arca testd siibguadrato-oblongd, lateribus rotun- 

 datis, postico latiore, inurgine ventrali bysso vix hiante ; rubido- 

 fuscd, epidermide fuscd setigerd indutd ; radiatim subtilissime 

 striatd, striis elevatis, granulosis; umbonibus siibapproximatis, 

 antice adjectis ; ligamenti ared angustd, declivi. 

 Conch. Icon. Arca, pi. 14. f. 94. 



Hab. Zanzibar (found under stones at low water) ; Thorn. 

 This species approaches very closely to Arca lacerata ; it appears, 

 however, to be of an uniform smaller size, the posterior side is less 

 expanded, and the bristles are set in single rows. 



Arca virescens. Arca testd elongatd, lateribus rotundatis, postico 

 leviter angulato, antico subattenuato ; viridescente, epidermide 

 . tenui, ad aream posticam setosd, indutd ; striis elevatis radiatd ; 

 ligamenti ared angustissimd, umbonibus approximatis. 

 Conch. Icon. Arca, pi. 15. f. 97. 



Hab. Catbalonga, island of Samar, Philippines (found under stones 

 at low \vater) ; Cuming. 



