﻿459 



Trocholites, but this is not sustained by closer approximation in the 

 early stages. The nepionic stage has whorls which depart more 

 widely from the- trocholitean form of the same age than the later 

 stages of growth. 



The umbilical perforation is large, the whorls are few in number 

 and increase less rapidly by growth and change more in form than 

 in Trocholites, the sutures are more sinuous, the siphuncle is not 

 so close to the dorsum, the apertures narrower in transverse and 

 longer proportionately in ventro-dorsal diameters and have deeper 

 narrower hyponomic sinuses, the living chambers are much shorter, 

 varying, so far as known, from less than one-fourth of a volution to 

 somewhat more than one-half of a volution, and the size is very 

 much greater at the same age in all dimensions and there are fewer 

 whorls. 



The resemblances consist in the surface ornamentation, which, 

 although much coarser, is similar to that of Trocholites. 



But even here the deep V-shaped dorsal sinus found in some 

 species is quite distinct. The aspect of the neanic stage before the 

 whorl acquires the flattened abdomen and sides is similar, but this 

 likeness becomes of less importance when the younger nepionic 

 stage is considered. The ananepionic substage may possibly have 

 very fine straight transverse striations, which are not usually visible, 

 but it is apparently smooth as seen in my specimens and in the 

 figures given by others.* The metanepionic stage has strong trans- 

 verse bands of growth with finer striae on the surface of the bands. 

 The borders of the bands are prominent and crenulated, the crenu- 

 lation being due to short longitudinal depression and intermediate 

 folds that occupy the edges of the bands and are discontinuous be- 

 tween them. 



The costations also begin to appear in this substage, and these 

 are in some species apparent as obscure folds on the casts. These 

 are distinct from the bands of growth being less numerous on the 

 surface and more widely separated. The crenulations disappear 

 subsequently probably before the completion of the second whorl, 

 but there are often a few continuous longitudinal raised lines per- 

 ceptible on the centre of the venter and near the umbilical shoulders. 

 The cyrtoceran form is retained longer in the nepionic stage than 

 in Trocholites and the change to the gyroceran curve that brings 



*See Schroeder's figure of Schroederoccras (Troch.) DamcsLPal. Abh. v. Fl. xxviii, Fig-. 2a. 



