214 



27. Mactra Californica, Conr. Journ. p. 240. pi. 18. f. 12. 

 Hab. la paludes limosas, inter fluxum maris, Sta. Barbara, varius. 



Mus. Gould. 



Allied to M. exoleta, but much smaller, flatter, and more trans- 

 verse. 



28. Mactra planulata, Conr. Journ. p. 240. 

 Hab. Uaa cura prsecedente. Mus. ? 



29. Petricola Californica, Conr. 



Saxicava Californica, Conr. Journ. p. 256. pi. 20. f. 9. 



Petricola Californica, Conr. Journ. Aug. 1849; Desh. B. M. Cat. 

 Ven. p. 208. no. 3. 



= Petricola arcuata, Desh. Rev. Zool. Cuv. 1839, p. 358. 



Hab. Sta. Barbara, San Diego, &c. Mus. Gould, Cuming. 



Var. = Saxicava carditoides, Conr. Journ. p. 255. pi. 20. f. 8: 

 =. Petricola carditoides, Conr. Journ. Aug. 1849. 



Conip. Petricola cylindracea, Desh. Rev. Zool. Soc. Cuv. 1839, 

 p. 358 ; B. M. Cat. Ven. p. 208. no. 5. 



The S. carditoides, constituted by Conrad for a single valve found 

 near Sta. Barbara, is regarded by hitn as identical with the P. cylin- 

 dracea of Deshayes. After a comparison of a large series of speci- 

 mens belonging to Dr. Gould and Mr. Cuming, I have, with Mr. 

 Nuttall's consent, united Conrad' s t\vo species ; retaining the latter 

 name, though least expressive, because already adopted by Deshayes 

 for his own P. arcuata. Dr. Gould regards both the P. arcuata 

 and P. cylindracea of Desh. as being identical with Conrad's P. car- 

 ditoides ; but I have not sufficient confidence that such is the case 

 to venture on uniting them. 



30. Rupellaria lamellifera, Conr. 



Fenus lamellifera, Conr. Journ. p. 251. pi. 19. f. 19. 



= Venerupis Cordieri, var. /3, Desh. B.INI. Cat. Ven. p. 191, no. 1, 



Petricola Cordieri, Desh. Rev. Zool. Soc. Cuv. 1839, p. 358; 

 Mag. Zool. pi. 18. 



Hab. San Diego. Mus. Cuming, Nuttall, Gould. 



On comparing the solitary vai ves on which Conrad's species was 

 founded, with a series of very variable specimens in Dr. Gould's and 

 Mr. Cuming's collections, there appears scarcely a doubt of its iden- 

 tity with that of Deshayes. 



31. ? Tapęs TUMiDA, Conr. 



T. t. subąuadrata, valde inceąuilaterali, alba, huc et illuc aurantio 

 punctata ; postice latiore, tumente ; costulis plurimis rotun- 

 datis radiantibus, haud e.vtanfibits, interstitiis subceąuantibus ; 

 liris concentricis satis confertis. rotundatis, secundum costas 

 pectinatis ; liyamento haud conspicuo, area minima, suleis dua- 

 bus circumeuntibus ; lunula minima, pai-um d ejinita ; dent. card. 

 in utraąue valva iii. valde divergentibus, cjuorum centrales, et 

 in valva altera posticus bifidi sunt ; margine cardinali interno 



