— 57 — 



Pecten discus Conrad. (PL V, Figs. 55, 56.) 



The original description and figure having been from a cast " beauti- 

 fully preserved in indurated clay" (which is a very unreliable kind of 

 specimen to describe, especially in this genus), I have here given figures 

 from shells found by Mr. Watts in Kern County. This is about ninety 

 miles northeast of the locality of its discovery, but the species found at 

 the two places are to a great extent the same. The present specimens 

 diflfer from the original type in having about three more ribs, in which 

 they are intermediate between that and P. deserii Con. (of which Mr. 

 Fairbanks also brought many good specimens from the Carrizo Creek 

 locality). Clay casts, like the original, are common in Ventura County, 

 and were collected by Dr. Bowers, but none with shell remaining were 

 found there. It seems likely that the species named will have to be 

 combined as one, the difi^erences being within the range of variation in 

 many other species. The internal view of the larger valve was neces- 

 sary, because it is so incrusted on the outside with hard rock that it 

 cannot be separated without probable fracture. The small one is about 

 equally convex on both sides, as in P. deserti. The original type very 

 much resembled the convex valve of Vola hella Con. 



Liropecten estrellanus Conrad. (PL V, Figs. 65, 67.) 



Pallium estrellanum Con., Pacif. R. R. Rept., vol. VI, 1850, p. 71, pi. 3, 

 fig. 15. Vol. VII, p. 191, pi. 3, figs. 3, 4. 



P. crassicardo Con., Proc. Phil. Acad. Nat. Sc, Dec. 1862, p. 291. 



Spondylus estrellanus Con., Pac. R. R. Rept., vol. VII, p. 191, pi. 1, 

 fig. 3. 



Liropecten estrellanus Con., L. crassicardo Con., L. volseformis Con., 

 Proc. Phil. Acad. Nat. Sc, 1862, p. 291. 



Pecten pahloensisf Con., Pac. R. R. Rept., VI, p. 71, pi. 3, f. 14. 



Specimens were collected by all the assistants in the Coast and San 

 Joaquin Valley counties, from Solano to Orange, Counties; also by Mr. 

 Lockwood, in Napa County, etc., showing every variation. 



Although Mr. Gabb admitted all four of Conrad's supposed species 

 here named, I am satisfied from much more and better materials than 

 he had, that they only represent various ages and conditions of only 

 one, or possibly two, if Pecten pahloensis can be maintained; if not it 

 will have priority as the specific name. The specimen figured shows 

 nearly all the characters of the various forms combined, admitting that 

 P. pahloensis is only the young stage. The ribs vary from sixteen to 

 nineteen, though given as seventeen in all except the last by Conrad, 

 who gives them as eighteen to twenty in that. The intermediate riblets 

 are at first one in each space, biit between the six anterior ribs on the 

 lower (right) valve and nine on the upper, they increase, as the shell 

 grows, to four and gix, the twa latter being on the sides of the ribs. 



