LOWER HELDERBERG ROCKS. 345 



Ortlioceras clavatuui ( n. s.). 



Plate LXXI. Fig. 4. 



The specimen is a fragment, preserving a part of the outer chamber and several 

 of the septa alxjve. The form is somewhat abruptly tapering, and dilfers from any 

 other species in tlie same group of strata. 



Geological position and locality. In the lower part of the pentamerus limestone : 

 Schoharie. 



Oitlioeeras ? 



Plate LXXI. Fig. 3. 



The specimen is marked by thin slightly convex septa; but having no others of 

 similar character, it can scarcely be characterized. 



The condition of the Orthocerata in this group of strata is usually very unsatis- 

 factory, all the species occurring in a fragmentary condition. 



Geological position and locality. In the pentamerus limestone : Schoharie. 



Ortliocera^ tenuiaiiiiulatuiu ( n. s.). 



Plate LXXII. Fig. 1. 

 Shell cylindrical, very gradually tapering : septa unknown. 

 Surface marked by thin abruptly elevated annulations, and by longitudi- 

 nal striae, with obscure indications of fine transverse strise. 



Fig. 1. A fragment, natural size. 

 Geological position and locality. In the shaly limestone of the Lower Helderberg 

 group : Albany county. 



Ortlioreras liclderbprgiae (n.s.). 



Plate LXXII. Fig. 2. 



Shell very gradually tapering ; section circular. Septa distant about one- 

 fourth the diameter of the shell ; convexity of the septa nearly equal 

 the space between them. Siphuncle small, central. Surface unknown. 

 fhe specimen figured is compressed, and the lines of septa obscure. In another 



specimen, preserving a part of the outer chamber and fifteen of the succeeding 



chambers, the characteristic features are well preserved. 



Geological position and locality. In the shaly limestone of the Lower Helderberg 



group : Carlisle and Schoharie, Schoharie county. 



[ PALiEONTOLOOY III.] 44 



