192 PALHONTOLOGY OF NEW-YORK. 
249. 1. TROCHOLITES AMMONIUS. 
PL. XL. A. Figs. 4a—-hk. 
Trocholites ammonius. Conran, Ann. Geol. Report, 1838, p.119. See also Generic description of Trocholites 
revised, in Jour. Acad. Nat, Science, 1842, Vol. vill, p. 274. 
— — Emmons, Geol. Report, 1842, pag. 372, fig. 4. 
Compare Lituites cornuarietis, SowERBy in Sil. Researches, 1839, pag. 643, pl. 20, f. 20, & Ib. pl. 22, f. 18. 
_ — Portiock, Geol. Rep. Londonderry, 1843, pag. 382, pl. 28 B, fig. 7 a, 0. 
— —_ VeRNEUIL, Pal. Russia and Ur. Mountains, 1845, pag. 359, pl. 25, fig. 7 a,b. 
— odini, Ip. Ib. pag. 361, pl. 25, fig. 8. Clymenia odini? Ercuwaup, 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 striz or ridges, between and 
upon which are finer lamellose strie, covering the outer surface, and giving it a peculiar 
textural or netted appearance ; striae 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 Lctuites cornuarietis of Sowrersy ; but if the one figured by pE 
VeERNEUIL is identical, our species presents some important variations. The strie 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 strie 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 lamella, 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 striae. The stronger strie are very variable, being sometimes 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 surface is marked only by the finer 
lamellose strie. 
Upon a careful examination of the figures and descriptions of Lituites odint of VERNEUIL 
(Clymenia of Ercuwatp ), I am satisfied that our species is closely allied, if not identical 
with that one, and that it is quite distinct from the L. cornuarietis of Russia. The strie 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. 
