198 fALJEONTOLOOY OF NEW-tORK. 



258. 11. ORTHOCERAS ARCUOLIRATUM (n. sp.). 



Vu. XLII. Figs. 7 o. b, c. 

 Camtrocerat' trentonensit (siphuncle), Conrad in MS. B^mons, Geol. Report, pag. 397, fig. 4. 



Slender, very gradually tapering to an acute point ; surface marked by strong and 

 extremely arching or undulating annulations, and, obscurely, by fine longitudinal striae ; 

 annulations about equalling the spaces between them ; outer chamber and aperture un- 

 known ; section circular ; siphuncle central. 



The distinguishing features of this species are its slender form and extremely arched 

 annulations, which, in half the circumference, ascend twice the width of the space between 

 each annulation. All the other annulated species have the ridges less arched upon the back. 



Fig. 7 a. A fragment near the apex of the shell. 



Fig. 7 b. A fragment of larger diameter, showing the convexity of a septum. 



Fig. 7 e. Transverse section, showing the central position of the siphuncle. 



Position aiui locality. This species occurs both in the lower shaly strata of this rock at 

 Middleville, and in the higher crystalline portions of the same rock at Watertown. 



{State CoUection.) 



259. 12. ORTHOCERAS TERETIFORME ( n. sp>). 

 Pl. XLII. Figs. 8 a, b. 

 Orthoctratile. Emmons, Geol. Report, 1842, pag. 396, fig. 3. 



Robust ; ttibe strong, somewhat rapidly tapering towards the apex ; outer cheimber and 

 aperture unknown ; surface marked by strong, slightly undulating annulations, the centres 

 of which are distant from each other about twice the diameter of the ridges, longitudinally 

 marked by coarse striae ; section circular ; septa having a convexity exceeding one third 

 the diameter of the tube ; siphuncle small, central. 



The specimens of this fossil which have been seen, are imperfect, and have only a 

 portion of the shell remaining, which preserves some strong longitudinal striae without any 

 visible finer markings. It differs from the preceding species in the stronger annulations, 

 which are less undulated than in that species ; the surface markings are also stronger, and 

 the tube enlarges more rapidly towards the aperture. 



The summit of the lower specimen is covered by the dorsal valve of Orthis testudinaria, 

 which gives an irregular convexity to the outline. 



• Blr. CoNBAi) {Jour. Acad. JiTat. Sci. Philadelphia, 1843, Vol. viii, p. 207 ) has proposed the generic name of 

 Cameroeerat for a species of Orthoceratite with a large lateral siphuncle, which exhibits strong oblique ridges at the 

 janctjon of the septa. This specimen is clearly septate within, and is therefore not the siphuncle. (See also Plate Ivi. 

 of this Report.) 



