20i2 PALEONTOLOGY OF NEW-YOKK. 
265. 18. ORTHOCERAS ANELLUM. 
Pl. XLIII. Figs. 6 a , b , c, d, e,f. 
Orthoceras anellus . Conrad, Proc. Acad. Nat. Sciences, 1843, Vol. i, p. 334. 
Elongated, very gradually tapering, annulated by prominent sharp slighlly sinuous 
ridges which are distant about one fourth the diameter of the shell, longitudinally marked 
by fine crowded wrinkled stries ; septa moderately convex ; siphuncle excentric, but not 
marginal ; section circular. 
This species is readily distinguished from any of the preceding by the angular approxi¬ 
mate annulations, which are sharper and more elevated than those of any other species 
known in the rock. The length of the larger fragment figured is one inch and a half: the 
diameter at the larger extremity is half an inch ; at the smaller end, three eighths of an 
inch. The smaller specimen differs from the other in the strice being less crowded, though 
otherwise similar. 
Fig. 6 a. A fragment of the septate portion of the shell, b. Transverse section of the same. 
Fig. 6 c. Enlarged portion, showing the striae, which, on a great part of the surface, are covered by a 
calcareous coating. 
Fig. 6 d. A smaller fragment, e. Transverse section, f. Portion of the surface enlarged. 
Position and locality. The larger specimen is from Mineral Point ( Wisconsin), where it. 
is associated with several other Trenton limestone species. The smaller specimen is from 
the lower part of the same rock at Middleville. {Cabinet of Mr. Conrad.) 
266. 19. ORTHOCERAS UNDULOSTRIATUM (n. sp.). 
Pl. XLIII. Figs. 7 a - k. 
Compare O. trochlearis, Hisinger, Leth. Suecica, pag. 28, pl. 9, fig. 7. 
Cylindrical, very gradually tapering, annulated by oblicpie undulating angular ridges, 
which are distant about one fourth the diameter ; annulations transverse on the ventral 
side, and abruptly arching towards the apex on the dorsal side ; surface marked by fine 
crowded transverse undulating strife ; section circular ; siphuncle slightly excentric. 
This species is readily distinguished from the others, by the transverse undulating striee 
without longitudinal lines. The annulations are subangular, and abruptly arched on the 
dorsal side, in this respect resembling the longitudinally striated species. In its external 
characters, it corresponds with 0. trochlearis of Hisinger ut supra ; but the position of the 
siphuncle is more nearly central, and the annulations more angular. 
This species may be confounded with 0. bilineatum , and the variety of that species, 
where the shell is removed ; but it differs from those, in the more angular character of the 
