590 REPORT— 1863. 



Tapes dwersum, Sby. [ = Tapes staminca, Conr., yar. PetUii, 



Desh.] Recent formation. San Pedro. 

 Saxicava ahrupta, Conr.,n.s. [Probably the shortened form of 

 Petricola carditoides, Conr.] Recent formation. San Pedro. 

 „ 24. 28. Petricola Pedroana, Com-., n.s. [Allied to P. ventricosa, Desh.] 

 Recent formation San Pedro. 

 rV. 33. 29. Schizotheerus NuttaUi,Com.,"n.s.''=Tresuscapax,Gli. Recent 



formation, San Pedro. 

 III. 23. 30. ?Lutraria Trashei, Conr., n.s. [Not improbably = Saxidomus 

 NuUaUii, Conr., jun.] PMiocene. Carmello. 

 V. 45. 31. Mactra Diegoana, Conr., n.s. Like M. albaria, of the Oregon 

 Miocene. [Resembles Midinia angulata, Gray.] P Miocene. 

 San Diego. 

 „ 35. 32. Modiolaconiracta, Com,, n.a. [Very like ilf. recto, Conr.] ? Mio- 

 cene. Monterey Co. Recent formation. 

 „ 40. 33. Mytilus Pedroanm, Conr., n.s. [Probably =ilf. edulis, jun.] 



Recent formation. San Pedro. 

 ., 41. 34. Pecten DeseHi, Conr., n.s. [Resembles P. circularis.] Mio- 

 cene. Carrizo Creek, Colorado Desert. 

 „ 34. 35. Anomia siibcostata, Ooni., n.s. [? = Placunanomia macroschisma.] 

 Miocene. Colorado Desert. Allied to A. Muffitii. 

 Ostrea vespei-tina, Conr., n.s. [Resembles O. lurida, var.J Mio- 

 cene. Colorado Desert. Like O. suhfalcata, Conr. 

 Ostrea Heermanni, Conr., n.s. Colorado Desert. 

 Penitella spelc^a, Com., n.a.* Recent formation. San Pedro. 

 Fisswella crenulata, Sby. \_=ljucapina c] Recent formation- 

 San Pedro. 

 VI. 52. 40. Ci-epidula princeps, Conr., n.s. [= C grandis, Midd.] Recent 

 formation. Santa Barbara. 

 V. 39. 41. Narica Diegoana, Conr., n.s. ? Miocene. San Diego. 



Trochita Diegoana, Conv., n.s. [hike T. ventricosa ; but may be 



Galencs contortus.'] PMiocene. San Diego. 

 Cnicihuhmi spinosum, Conr., n.s.t Recent formation. San Diego. 

 VI. 49. 44. Kassa interstriata, Conr., n.s. [=iV. mendica, Gld.]. Recent 

 formation. San Pedro. 

 „ 48. 45. Kas^a Pedroana, Conr., n.s. [Comp. Amycla gausapata and its 



congeners.] | Recent formation. San Pedro. 

 „ 51. 46. Strephona Pedroana, Conr., n.s. [Comp. Olivella beetica.'] Recent 



formation. San Pedro. 

 „ 50. 47. Idtorina Pedroana, Conr., n.s. [_= L. plena, GIA.'] Recent forma- 

 tion. San Pedro. 

 „ 47. 48. Stramonita petrosa, Conr., n.s. [Is perhaps Monoceros lugubre.] 

 ?—. Tulare Valley. 



* Mr. Conrad regards the " coriaoeous cup as characteristic of the genus.'' It appear: 

 R subgenus of Fholadidea, differing m the form of the plate. Mr. Tryon, " Mon. Pho 

 lad.," p. 66, restricts it to the Penitella penita, which (according to his diagnosis) hai 

 > one central and two anterior dorsal plates. The closely related P. ovoidea he leaves iri 

 the original genus, as having "tvpo dorsal accessory valves," although he allows that "its 

 position cannot be accurately determined on account of the loss of its dorsal valves." 

 Conrad's fossil has the shape of P. ovoidea ; but although he says that it is " widely dis- ■ 

 tiuct" from P.penita, I am unable to separate it from the ovoid form of that species, 

 which will be found in the Smithsonian series. 



t This is certainly Sowerby's species, to which Conrad gives a doubting reference. In 

 the text he gives it as " spinosum, Conr.," in his table marking it as " nov. sp." 



J Conrad compares N. interstriata to N. trimttata, Say, and N, Pedroana toZf. lundtd. 

 Say, and states that the two Atlantic species are " associated with each other both in the sea 

 and in the Miocene deposits of Virginia and Maryland." As the two correlative species 

 ore found together, living and fossil, on the Pacific side, there is presumptive evidence for 

 tiieir having descended from a common stock. 



76 



