PLATE 64. 



Fig. 1. 660. 37. Orthoceras undulatum. ( Pag. 293.) 



1 a. A fragment of this species on a slab of sliale. 



1 i. Anotlier fragment wliere tlie laminae are nearly obsolete. 



1 c. A fragment repliiced by gypsum, and preserving only the annulations. 



1 d. A fragment near the smaller extremity, showing the lamina but partially preserved. 



1 e. Transverse section of an imperfect and somevphat distorted specimen, showing the position of the 



siphuncle. 

 1 /. Vertical section showing the convexity of a seiDtum. 



