590 REPORT —18638. 
Plate Fig. No. 
IV. 31. 26. Tapes diversum, Shy. [= Tapes staminea, Conr., var. Petitii, 
(IIL. in text). Desh.] Recent formation. San Pedro. 
Il. 25. 27. Sazxicava abrupta, Conr.,n.s. [Probably the shortened form of 
Petricola carditoides, Conr.| Recent formation. San Pedro. 
24. 28. Petricola Pedroana, Conr., n.s. [Allied to P. ventricosa, Desh. ] 
Recent formation San Pedro. 
{V. 33. 29. Schizotherus Nuttalli, Cony., “n.s.” = Tresus capax, Gid. Recent 
formation. San Pedro. 
Ill. 23. 30. PLadraria Traskei, Conr., ns. [Not improbably = Saxidomus 
Nuttallii, Cony., jun.| Miocene. Carmello. 
V. 45. 31. Mactra Diegoana, Conr.,n.s. Like M. albaria, of the Oregon 
Miocene. [Resembles Mulinia angulata, Gray.] ? Miocene. 
San Diego. 
» 35. 82. Modiola contracta, Conr.,n.s. [Very like M. recta, Conr.] ? Mio- 
cene. Monterey Co. Recent formation. 
» 40. 383. Mytilus Pedroanus, Conr., u.s.  [Probably=M. edulis, jun.) 
Recent formation. San Pedro. 
» 41. 34. Pecten Deserti, Conr., n.s. _[Resembles P. ctreuaris.] Mio- 
cene. Carrizo Creek, Colorado Desert. 
» 84 35, Anomia subcostata, Conr.,n.s. [P= Placunanomia macroschisma. | 
Miocene. Colorado Desert. Allied to A. Ruffini. 
5» 36-38, 36.  Ostrea vespertina, Cony., n.s. [ Resembles O. lurida, vax.| Mio- 
,cene. Colorado Desert. Like O. subfalcata, Conv. 
37. Ostrea Heermanni, Cony.,n.s. Colorado Desert. 
» 43. 38. Penitella spelea, Conr., n.s.* Recent formation. San Pedro. 
44. 39. Fissurella crenulata, Shy. [=Lueapina 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., ns. [Like 7. ventricosa; but may be 
Galerus contortus.| ?Miocene. San Diego. 
46. 43. Crucibulum spinosum, Cony.,n.s.+ Recent formation. San Diego. 
VI. 49. 44. Nassa interstriata, Conr., ns. [=N. mendica, Gld.]. Recent 
formation. San Pedro. 
» 48. 45. Nassa Pedroana, Conr.,n.s. [Comp. Amycla gausapata and its 
congeners.|{ Recent formation, San Pedro. 
» 51. 46. Strephona Pedroana, Conr.,n.s. [Comp. Olivella betica.] Recent 
formation. San Pedro. 
» 50. 47. Litorina Pedroana,Conr.,u.s. [=L. plena,Gld.| Recent forma- 
tion. San Pedro. 
» 47. 48, Stramonita petrosa, Conr.,n.s. [Is perhaps Monoceros lugubre. | 
P—. Tulare Valley. 
” 
* Mr. Conrad regards the “ coriaceous cup as characteristic of the genus.” It appears 
a subgenus of Pholadidea, differing in the form of the plate. Mr. Tryon, “ Mon. Pho- 
lad.,” p. 66, restricts it to the Penitella penita, which (according to his diagnosis) has 
one central and two anterior dorsal plates. The closely related P. ovoidea he leaves in 
the original genus, as having “two 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- 
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. 
+ This is certainly Sowerby’s species, to which Conrad gives a doubting reference. In 
the text he gives it as “ spinoswm, Conr.,” in his table marking it as “ nov, sp.” 
+ Conrad compares NV. interstriata to N, trivittata, Say, and N. Pedroana to N. lunata, 
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 
are found together, living and fossil, on the Pacific side, there is presumptive evidence for 
their having descended from a common stock. 
