71 



catd dimidiatis ; areis, anticd oblique divisd, parte posticd dorsali 

 radiathn cornigatd, parte anticd ventrali tenuiore, injlatd ; po- 

 sticd longitudinaliter striatd, postice epidermide nigrd indutd ; 

 margine dorsali anticd injiato-reflexd ; valvis accessoriis duabus, 

 posticis, subtrigonis, superne fornicatis : long. 1-4, lat.0 15, 

 alt. 0-8 poll. 



Hub. ad Montem Christi, Columbise Occidentalis. 



Found in hard clay at low water. — G. B. S. 



Pholas tubifera. Phol. testa oblongd, postice subattenuatd, sub- 

 truncatd, antice rotundatd; valvis fascid transversim sulcatd di- 

 midiatis ; areis, anticd oblique divisd, parte posticd dorsali radi- 

 atim sulcatd, decussatd, parte anticd ventrali tenuiore, subin- 

 flatd ; posticd longitudinaliter striatd ; margine dorsali anticd 

 reflexo-inflatd ; valvis accessoriis dorsalibus duabus, posticis, sub- 

 ovatis ; epidermide postice in duas valvas planulatas decurrente, 

 deinde tubulum calcareum ad extremam partem conspicuum : long. 

 1-3, lat. 0-5, alt. 0-45 poll. 



Hub. ad Sinum Caraccensem, Columbise Occidentalis. 



Obs. Testa intermediae setatis tubulum caret. 



Found in decayed wood dredged up at ten fathoms' depth. 



A marked resemblance may be easily traced between this and the 

 Pholas papyracea of Southern Devonshire. 



Pholas Quadra. Phol. testd oblongd, tenuissimd, antice inflatd, 

 rotundatd, postice subattenuatd, subtruncatd; valvis fascid trans- 

 versim sulcatd dimidiatis ; areis, anticd oblique divisd, parte posticd 

 dorsali concentrice lamellosd, lamellis squamuliferis, parte an- 

 ticd ventrali tenuiore, inflatd, radiatim obsolete costellatd; po- 

 sticd longitudinaliter sulcatd ^ margine dorsali anticd concavo- 

 reflexd, musculum recipiente, epidermide obtectd ; epidermide 

 postice in vesiculas quatuor, undique duas, decurrente ; deinde tu- 

 bulum calcareum ad extremam partem conspicuum : long. 1*, lat. 

 0-3, alt. 0-3 poll. 



Hab. ad Montem Christi, Columbiae Occidentalis. 



Found in stones at low water. — G. B. S. 



Pholas Quadra, var. Phol. Quadra, testd parvd, margine dorsali 



anticd inflato-reflexd. 

 Hab. ad Montem Christi. 



This variety differs only in the circumstance of the epidermis 

 which covered the muscle contained in the concave reflected ante- 

 rior dorsal margin being changed into calcareous matter. The 

 young shells are without any tube or other accessory parts. — 

 G. B. S. 



Pholas curta. Phol. testd ovali, postice acuminatd, antice ro- 

 tundatd; valvis fascid transversim sulcatd dimidiatis ; areis, an- 

 ticd oblique divisd, parte posticd dorsali longitudinaliter striatd 

 et radiatim corrugatd, parte anticd ventrali tenuiore, subinflatd ; 



