LOWER HELDERBERG ROCKS. 335 



Platjceras oloiioatuiu ( n. s.). 



Plate LXIV. Fig. 6 & 10. 



Shell elongate-conical, straight or slightly bent near the apex, which is 

 central or subcentral : aperture somewhat rounded. 



Surface cancellated by undulating transverse lamellose striae and lon- 

 gitudinal rounded striae, which, in the partially worn surfaces, are of 

 nearly equal strength. One or two longitudinal undulations mark the 

 surface, but there are no distinct plications. 



This species is much more elongated and more nearly straight than the preceding 

 one, and the surface is free from distinct plications. 



Fig. 6. A young gpecimen of this species. 



Fig. 10. A large individual from which the extremity of the apex is broken, and the shell 

 partially exfoliated from the lower part. 



Geological position and locality. In the shaly limestone : Schoharie county. 



Platjceras eIoii(^atuiii? var, 



Plate LXV. Fig. 5 a, 5. 



Shell slightly arcuate, tapering very gradually above, with a few obscure 



undulations towards the base. 

 Surface cancellated by transverse and longitudinal striae. 



The specimen figured, with another of similar character, present some deviations 

 from the specimen fig. 10, Plate lxiv, and appear never to have been so extremely 

 elongated, and are also a little curved, while that one is rigidly straight except near 

 the apex. 



Fig. 5 a. A fragment of a specimen, natural size. 

 Fig. 5 6. An enlargement of the surface striae. 



Geological position and locality. In the upper part of the shaly limestone of the 

 Lower Helderberg group : Schoharie county. 



