590 REPORT 1863. 



Plate Fig. No 



IV. 31. 20. Tapes diversum, Sby. \_= Tapes stanwica, Conr., var. Peiiiii, 

 (III. in text). Desh.] Recent formation. San Pedro. 



III. 25. 27. Saxicava abrupta, Conr., n.s. [Probably the shortened form of 



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

 n 24. 28. Petricola Pedroana, Conr., n.s. [Allied to P. ventricosa, Desh.] 

 Recent formation San Pedro. 



IV. 33. 29. Schizothcerm Nuttalli,Com.,"n.s"=Tresus cajwx, Gld. Recent 



formation. San Pedro. 



III. 23. 30. ?Lutraria Traskei, Conr., n.s. [Not improbably = Stundomtts 

 Nttttallii, Conr., jun.] PMioceue. Camiello. 



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



Miocene. [Resembles Mulinia angulata, Gray.] ? Miocene. 

 San Diego. 



35. 32. Modiolac(mtracta,ConT.,-n.s. [Very like M. recta, Conr.] ? Mio- 

 cene. Monterey Co. Recent formation. 



40. V 33. Mytilus Pedroanus, Conr., n.s. [Probably M. edulis, jun.] 

 Recent formation. San Pedro. 



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

 cene. Carrizo Creek, Colorado Desert. 



34. 35. Anomia sttbcostata, Conr., n.s. \? = Placunanomia macroschisma.~] 

 Miocene. Colorado Desert. Allied to A. Ruffini. 



n 36-38. 33. Ostrea vespertina, Conr., n.s. [Resembles O. lurida, var.] Mio- 

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

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



43. 38. Penitella spelcea, Conr., n.s.* Recent formation. San Pedro. 



,, 44. 39. Fissurella crenulata, Sby. [=Lucapina c.~] Recent formation. 



San Pedro. 



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

 formation. Santa Barbara. 



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



42. 42. Trochita Diegoana, Conr., n.s. [Like T. ventricosa j but may be 

 Galerus contortusJ] PMiocene. San Diego. 



46. 43. Crucibulum spinosum, Conr., n.s.t Recent formation. San Diego. 

 VI. 49. 44. Nassa interstriata, Conr., n.s. [=JVi mendica, Gld.]. Recent 

 fonnation. San Pedro. 



48. 45. Nasta Pedroana, Conr., n.s. [Comp. Amycla gausapata and its 

 congeners.] J Recent formation. San Pedro. 



51. 46. Strephona Pedroana, Conr., n.s. [Comp. Olivetta baticaJ] Recent 



formation. San Pedro. 



. 50. 47. Litorina Pedroana, Conr., n.s. \_=L. plena, Gld.] Recent forma- 

 tion. San Pedro. 



n 47. 48. Stramonita petrosa, Conr., n.s. [Is perhaps Monoceros lugubre.~\ 

 ?. Tulare Valley. 



* Mr. Conrad regards the " coriaceous cup as characteristic of the genus." It appear 

 a subgenus of Pholadidea, differing in the form of the plate. Mr. Try on, " Mon. Pho 

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

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

 the original genus, as having "two dorsal accessory valves," although lie 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- 

 tinct" 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. trivittata, Say, and N.Pedroana toN. lunatd, 

 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 

 8^*0 found together, living and fossil, on the Pacific side, there is presumptive evidence for 

 their having descended from a common stock. 



76 



