422 A. HYATT — TRIAS AND JURA IN THE WESTERN STATES. 



There is a close representation of the American species among Russian 

 forms usually referred to Cardioceras alter nans, since such representatives 

 as the one figured by D'Orbigny* under the name oi Ammonites subcor- 

 diatus have young with single costse and compressed whorls like those of 

 Cardioceras dubium. The specimens of aJternans figured by Rouillier f are 

 both distinct from that figured by D'Orbigny. That figured first on 

 plate I has alternate and bifurcated costse like the alternans of more 

 southern localities. 



It is a notable fact that in the Russian fauna Aucella makes its appear- 

 ance in the Oxfordian in company with Cardioceras alternans, and one of 

 the three sjoecies which first appears, Aucella bronni, is that which is con- 

 sidered by Lahusen to be the representative of our Aucella erringtoni^ 

 Meek. 



j?,^',' Perisphhinctes virgidatiformis, n. s. 



Loc, Stanislaus river, opposite Bostwicks barj near Reynolds ferry, and 



also opposite to Bear creek. 



P. virgidatiformis has the peculiar closely approximated linear costse of 

 a group of Perisphinctes which occurs only in the Upper Jura throughout 

 western Europe. This species is not a typical discoidal form of Peri- 

 sphinctes. The whorls are decidedly involute, the inclusion being about 

 one-third, and although the inner whorls are discoidal until a late stage 

 and the umbilicus is what one would term open, still the outer whorl 

 broadens rapidly. 



There are several close allies in the Upper Jura of Europe. One of 

 these is Ammonites virgulatus, Quenstedt, of the Oxfordian ; another and 

 perhaps even closer form is his Ammonites planulatus siliceus which 

 occurs in the Solenhofen schists. All of these differ from our species 

 in the regularity with which the pilse bifurcate, and probably the whorls 

 of our species may differ somewhat in outline of a transverse section, 

 but this cannot be ascertained on account of the compression of. the 

 specimens in hand. The sutures agree closely and show that these forms 

 are all allied species of the same group. 



C jeremejevi Nikitin of the Russian fauna § is a similar form, and 

 only every alternate costation is bifurcated, so that it comes very near to 

 the American shell, in which the bifurcation is irregular. Some of our 

 examples have hardly any of the costse bifurcated ; others have only a 

 few with bifurcations, but in some specimens every alternate costse is 



* Russia and the Ural, Murch. De Vern , etc, Pal. I, pi. 25, fig. 3. 

 t Bull. Soe. Nat. de Moscow, 1849, p. 362, pi. I, fig. 88, pi. M, fig. 109. 



X Dr. Curtice describes this locality as "on trail south side of and opposite great bend of river 

 by Reynolds ferry, road from Copper town to Sonora." 

 jiCeph. d Gouv. Kostroma, pi. 4. 



