194 PALJEONTOLOGY OF NEW-YORK. 



251. 2. CYRTOCERAS ANNULATUM (n. sp.)- 



Pl. XLI. Figs. 4 a, b, c, il ; and Fig. .5. 



Gradually curving, expanding towards the aperture ; surface annulated by strong ridges, 

 which, with the intermediate spaces, are marked by fine transverse strife ; siphuncle 

 central ; septa jjlain. 



This species is readily recognized among all the others, at present known, in this rock, 

 by its elevated annulating ridges and fine striee, in which it is very similar to some of the 

 Ortliocerata. The shell is pretty uniformly curved, gradually enlarging, and more abruptly 

 expanding towards the aperture. It occurs in fragments, a perfect specimen not having 

 been seen. The central position of the siphuncle is a departure from the usual character of 

 Cyrtoceras, and on this account may be regarded as a bent Orthoceras ; but it enlarges 

 more rapidly towards the aperture than ordinary species of that genus, and being constant 

 in its curvature, this may be regarded as its normal form. 



Fig. 4 ffl. A large fragment, which is a cast, retaining the annulations. 

 Fig. 4 b. A smaller fragment, retaining the shell and transverse strife. 

 Fig. 4 c. Section of the last, showing the siphuncle. 

 . Fig. 4 d. A portion of the surface magnified. 

 Fig. 5. A fragment of the same species, nearer the aperture. 



Position and locality. In the lower shaly strata at Middleville, and in the higher crystal- 

 line strata of the same rock at Watertown. (State Collection.) 



252. 3. CYRTOCERAS MACROSTOMUM. 



Tl. XLII. Figs. 1 a, 4, c, & 3 a, b. 



Cyrtoceras marginalis. Conrad, Proc. Acad. Nat. Sciences, 1843, Vol. i, p. 334. 

 Not Cyrtoceras marginahy Phillips, Pal. Fossils, 1841, pag. 115, pl. 4(j, fig. 219. 



Subconical, slightly incurved, rapidly enlarging from the apex ; outer chamber large, 

 forming about half the length of the fragment ; septa closely arranged ; siphuncle dorsal i 

 section not entirely circular ; surface 1 



The fragment measures four inches, the outer chamber occupying one half the length. 

 There are twenty-five septa remaining in the portion preserved. The diameter of the smaller 

 extremity is half an inch ; and of the larger, one inch and seven-eighths, the edge being 

 broken. The septa are interrupted, and slightly bent upwards along the dorsal line, by (he 

 siphuncle. The elliptical form of the section is due to pressure, the natural form being 

 circular. 



The larger specimen described is from Wisconsin, where it occurs associated with Trenton 

 limestone fossils. Fraginents of the same have been seen in New-York and in Pennsylvania. 

 The fragment 3 c i is probably of the same species, since a careful examination shows that 

 it is not identical with Zed. This specimen is marked by closely arranged lamellose stria?, 



