DESCRIPTIONS OF UPPER JURA FOSSILS — AMMONITIN^. 423 



bifurcated on parts of the whorl. It seems probable that the American 

 species had rounder whorls than P. jeremejevi. 



/^2^^o .^Perisphinctes, sp. (?) 

 Loc, Stanislaus river, opposite Bostwicks bar, near Reynolds ferry. 



This is a form of Perisphindes with the lateral ribs w^ell separated, as in 

 most species of the genus found to the west of the Sierras. The whorl 

 is broader at the same age than in any other species mentioned in this 

 paper ; there are consequently fewer whorls at the same age. The lateral 

 costse are single and very long, the bifurcations occurring well up on the 

 abdomen. 



Perisphinctes, sp. (?) 

 Loc, south bank of Tuolumne river at Moffats bridge ; Stanislaus river, 

 near canyon opposite mouth of Bear creek ; and six miles from 

 Copperopolis on road to Sonora and grade to Angels creek. 



There are several fragments collected by Dr Curtice at these three 

 localities which probably represent more than one species, but there is 

 nothing to indicate the age of the rocks forther than that they are high 

 up in the Jurassic. 



7o'U' '^ Periiiph in ctes filiplex (?) 



Ammonites filipl ex, Quenstedt. Ammonites d. Schwab. Jura, vol. iii, pi. 



126, fig. 3. 



Loc, south bank of Tuolumne river at Moffats bridge, and Stanislaus 



river near canyon opposite Bear creek. 



The fragments representing this form are interesting because they ex- 

 hibit in a marked manner the ])eculiar widely separated, single lateral 

 costa3, regularly bifurcated on the abdomen, of the group of Perisphindes 

 alternans from the Upper Jurassic of Russia which is mentioned at the 

 end of the description of P. colfaxi. The fragments are, however, so 

 closely similar to the Ammonites filiplex of the Solenhofen slates that I 

 have ventured to place them provisionally under this name. 



There are no tubercles on the lateral costa? in any of these specimens? 

 nor are there any indications of affinity with species of Olcostepjhanus, 

 although they otherwise closely simulate the gerontic (senile) whorls of 

 some species of that genus. 



The fragments of this species show that it reached a large size, and the 

 characteristics are extremely close in the adult stage to those of the 



