579 
was the first to state that most of our Western forms of Heteroceras 
probably had similar irregularities in the development of the last 
volution. 
Emperoceras,* n. g. 
The young are hamites-like, so far as known in the neanic stage 
and become helicoceran in the ephebic stage. It is not positively 
known that they have an extended gerontic stage. 
EMPEROCERAS BEECHERI. 
Loc., Near Buffalo Gap, S. Dakota. 
This species has, in the earliest substage, observed probably the 
metaneanic straight volution with straight coste, having each two 
minute tubercles on the venter, and no intermediate untuberculated 
and single coste. The section is compressed oval, the dorsum 
broader than the venter. The siphuncle is certainly in the mesal 
plane between the rows of ventral tubercles in this substage. The 
sutures are simple and appear to be symmetrical, or more nearly so 
than in the succeeding substages. 
The paraneanic is introduced when the hamites-like first bend of 
this specimen is made, and is terminated by a permanent constric- 
tion in the elbow of the second bend in both specimens of this 
species. Bifurcated costz appear and intermediate untuberculated 
costz in this substage. 
The next arm, probably the anephebic substage, is bent more or 
less Gownwards, but the curvature is distinct from that of the met- 
ephebic stage, and the form of volution in section is still a depressed 
oval, although much more gibbous on the upper than on the lower 
side. The section is that of a compressed ellipse, the ventrodorsal 
diameters increasing faster than the transverse. 
The intermediate single costz running uninterruptedly across the 
venter are more numerous in this substage, occurring from one to 
three between each bifurcated and tuberculated costation. The 
bifurcations are not always well marked, but they are more distinct 
than those given in the drawings, and here and there a costation 
may be single and have tubercles. ‘This volution begins to twist in 
the metephebic substage, and the asymmetrical helicoceran form is 
fully developed in the flattening of the lower side and the increas- 
ing gibbosity of the upper side, whether this be right or left, and 
the tubercles are correspondingly deflected. The siphuncle has 
x Epxnpos, deformed. 
