﻿473 



shown in Whitfield's figure, PL xxxii, and in my figure, the oldest 

 sutures are more sinuous than those of an earlier stage just under 

 the free part of -the living chamber, as given in my copy of his 

 figure, with sutures drawn in from the original chambers (Fig. 28, 

 PL vi). They have normally in the ephebic stage ventral and 

 dorsal lobes, with lateral lobes and saddles at the abdominal angles 

 and umbilical shoulders. 



The length of the living chamber in a full-grown specimen is 

 over one-half a volution, and the latter part is free, as given by 

 Whitfield and in my Fig. 7, PL vii. 



SCHROEDEROCERAS CASINENSIS. 



Lituites Eatoni, var. Casinensis. Whitf. (Buliet. Am. Mus., 

 New York, i, No. 8, PL xxxii). PL vi, Figs. 36-38, and PL 

 vii, Figs. 4-6. 

 Loc, Fort Cassin, Lake Champlain. 



This is a distinct species, the sutures being straighter in the 

 ephebic stage than in true Eatoni, the venter and sides are more 

 decidedly flattened, and the relative proportions of the last whorl 

 at the same age different.* The ventro-dorsal and transverse 

 diameters are about equal, whereas in Eatoni the transverse is con- 

 siderably longer than the ventro-dorsal in the mesal plane. The 

 amount of involution in Eatoni and the depth of the contact furrow 

 in the ephebic stage is also greater. 



Whitfield's figure is given on PL vi, Fig. 36, with some emen- 

 dations taken from the original specimen. This shows that the 

 ephebic stage had not a free living chamber, and that shown in my 

 Fig. 4, PL vii, represents the gerontic stage. The front view, 

 Fig. 5, shows the deeper contact furrow and the dorsal lobes in 

 the dorsum of the metephebic substage and the slight but imper- 

 ceptible change which takes place in the broader, shallower zone of 

 the early part of the gerontic living chamber below. The free 

 part of this chamber is at first concave just beyond the broken end 

 of the metephebic whorl, then flattened, and finally convex on the 

 dorsum, as shown in Figs. 5 and 6. 



The length of this living chamber was nearly three-fourths of a 

 volution, beginning somewhat beyond the broken part given in 



♦Whitfield himself thought this was probably a distinct species, as shown by his 

 remarks on page 332. 



