192 PALiEONTOLOGY OF NEW-YORK. 



249. 1. TROCHOLITES AMMONIUS. 



Pl. XL. A. Figs. ia-k. 



Trocholites ammonius. Conrad, Ann. Geol. Rppoit, 1S3S, p. U9. See also Generic description of Trocholites 



revised, in Jour. Acad. Nat, Science, 1812, Vol. viii, p. 274. 



— Emmons, Geol. Report, 1842, pag. 372, fig. 4. 



Compare Lituites cornuarittis, Sowerby in Sil. Researches, 1839, pag. 643, pi. 20, f. 20, & lb. pi. 22, f. 18. 



— PoRTLocK, Geol. Rep. Londonderry, 1843, pag. 382, pi. 28 B, fig. 7 a, b. 



— Verneuil, Pal. Russia and Ur. Mountains, 1845, pag. 359, pi. 25, fig. 7 a,b, 



— odini. Id. lb. pag. 301, pi. 25, fig. 8. Clymenia odini? Eichwald, 1840. 



Discoidal ; volutions in the same plane, about four, rounded, slightly concave on the 

 ventral side, gradually enlarging in size towards the aperture, which is slightly expanded ; 

 surface marked by lamellose irregular and oblique transverse stria? or ridges, between and 

 upon which are finer lamellose striffi, covering the outer surface, and giving it a peculiar 

 textural or netted appearance ; strife meeting in an arch upon the back ; septa direct, or 

 slightly undulated on the dorsal side ; outer chamber large ; siphuncle ventral. 



This is a very beautiful and interesting shell, and its usual appearance is very correctly 

 represented in the figures. In examining a large number of specimens, I have never found 

 one where the last volution extended in a direct line. I have been inclined to regard our 

 species as identical with Lituites cornuarietis of Sowerby ; but if the one figured by de 

 Verneuil is identical, our species presents some important variations. The strife meet in 

 an arch upon the back, and not in an acute angle forming a V as in the latter. In a single 

 injured specimen, however, I have detected a few of the strise near the aperture, meeting 

 in this manner upon the back, while the others present the usual appearance. The peculiar 

 character of the surface is produced by the numerous crowded edges of lamellee, which, 

 in perfect specimens, are somewhat regularly undulating. When the shell is partially 

 exfoliated, the textural character of the surface is destroyed, and it is only marked by fine 

 oblique striffi. The stronger striaj are very variable, being soinetimes so prominent as to 

 deserve the name of ridges, and at other times are only slight undulations ; while in many 

 instances they are not at all developed, and the smface is marked only by the finer 

 lamellose striae. 



Upon a careful examination of the figures and descriptions o{ Lituites odini of Verneuil 

 {Clymenia of Eichwald ) , I am satisfied that our species is closely allied, if not identical 

 with that one, and that it is qtiite distinct from the L. cornuarietis of Russia. The striiE of 

 L. odini are arcuate upon the back, precisely as in our specimens ; the septa are likewise 

 slightly undulating or bent towards the aperture on the back, particularly those of the inner 

 volutions ; and the whole aspect of the shell is decidedly like the New- York specimens, 

 •where the outer surface is exfoliated. In the Russian specimen, however, the siphuncle is 

 not represented so close to the ventral side of the volution as it is in our specimens. This 

 may happen in the last volution, where it is produced in a direct line, and less appressed 

 on the ventral side by contact with the inner ones. 



