1888, ] 241 [Keyes 
Recapitulating the salient features relative to Platyceras as here pre- 
sented, it appears: (1) that many, if not all, of the Platycerata were sta- 
tionary during life; (2) that the nourishment of these gasteropods was 
derived in great part at least from the excrementitious matter of the 
crinoid ; and (3) that the forrn of the peristome and its marginal configu- 
ration, being dependent upon the surface of attachment, have small value 
as characters for specific distinction. The first and third of these propo- 
sitions are consonant with observations made upon living Calyptreeide, 
while the second does not seem to present in this group any living ana- 
logue, and this fact is indicative of perhaps a wider separation generically 
of Platyceras and Cupulus than has hitherto been considered. 
The species of Platyceras in which sedentary habits are positively 
known from the attachment of the gasteropods to foreign bodies, are : 
Platyceras equilaterum Hall, P. infundibulum M. and W. 
P. parasiticum (Trautschold), P. chesterense M. and W. 
P. erectum Hall, P. dumosum Conrad, 
P. formosum Keyes, and five undetermined species. 
IV. Desorrerions or Four New Sprrcius or PLATYCERAS FROM THE 
LowEr SUBCARBONIFEROUS OF Iowa. 
Platyceras capaa, nov. sp. (Plate, figs. 14 and 15). 
Shell below medium size, ovate, subspiral, forming scarcely one volu- 
tion, rapidly and regularly expanding, both transversely and in the 
opposite direction, to the aperture. Apex small, obtuse, free, but more or 
less incurved toward the body of the shell, which is strongly arcuate ; 
very slightly deflected dextrally. Aperture nearly circular in outline, 
margin attenuated, and but slightly sinuous. Surface marked by distinct, 
often somewhat imbricated lines of growth. 
Horizon and locality. Burlington limestone near Burlington, Iowa. 
This species approaches, nearer than any other, some forms of P. aquil- 
aterum of Hall from the Keokuk limestone, but differs in having the body 
of the shell more arcuate and in uniformly expanding much more rapidly 
in the direction of the longitudinal diameter of the aperture. The apex 
is also farther removed from the body of the shell than in the Keokuk 
species, and there is no indication of longitudinal folds. 
Platyceras obliquum, nov. sp. (Plate, figs. 12 and 13). 
Shell of medium size, irregularly oblong, subspiral, forming one volu- 
tion, regularly enlarging, slightly more rapidly transversely than in the 
opposite direction, to the aperture. Apex large, obtuse, far removed from 
the body of the shell, which is broadly arched ; very noticeably oblique 
to the plane of general curvature in the body of the shell. Aperture 
irregularly quadrangular in outline ; lip sharp, and more or less sinuous. 
Surface marked by several undefined longitudinal plications, which some. 
times form longitudinal series of obscure nodes; these are crossed by 
numerous sinuous often subimbricated lines of growth. 
Horizon and locality. Limestones of the Upper Burlington at Burling- 
ton, lowa. 
