﻿462 



little too narrow in the figure on account of the necessary restora- 

 tion, and the ventral sinus is somewhat too narrow and too deep 

 owing to a mistake of the artist. The impressed zone continues on 

 the free part of the living chamber, but becomes distinctly shallower 

 and is almost obliterated in the dorsal outline of the aperture. 



SCHROEDEROCERAS SAEMANNI. 



Lituites angulatus Saem. (Paleon., iii, PI. xxi. Fig. ic-d ; not Fig. 



Loc, Brevig, Norway. 



The two specimens used by Saemann, one for his section Fig. id, 

 and other for the siphuncle, Fig. ic, are both in the collection of 

 the Mus. Comp. Zoology and cannot be considered identical with 

 Lituites angulatus (Figs. la-b). 



The characteristic differences have been noted under description 

 of that species. The abdomen of the ephebic stage is flat and 

 slightly convex, broader than the dorsum, and the sides are slightly 

 flattened in the full grown as in the Saemann's Fig. id, which was 

 taken from the exposed last septum or floor of a living chamber in 

 the metephebic substage on the last quarter of the third volution, a 

 substage preceding that in which the whorl became free, which I 

 have considered as the parephebic substage. The sides incline in- 

 wards and the umbilical shoulders are hardly perceptible. 



There is an impressed zone broader and deeper than in Schroedero- 

 ceras angulatum. The sutures are similar, but have a broader ven- 

 tral, dorsal and lateral lobes. The saddles on the abdominal 

 angles and those at the lines of involution are also narrower. 



The siphuncle is propiodorsan on the first quarter of the fourth 

 volution, as figured by Saemann. It is nearer the dorsum in the 

 younger whorl, being less than its own diameter distant from that 

 side on the early part of the third quarter of the second whorl. 



The sides are gibbous and the abdomen rounded throughout the 

 earlier whorls until the beginning of the third whorl in the anephebic 

 substage. 



The ventrodorsal diameters increase by growth more rapidly than 

 in angulatum, and the whole shell is consequently larger at corre- 

 sponding stages of development. 



The living chamber is longer as well as in every way larger on 

 the third whorl in the anephebic substage before the free part of the 

 whorl is reached, than it is in angulatum at a later age in the early 

 part of the parephebic substage as figured by Saemann. In this 



