ENGONOCERATID. eal 
The venter in this species remains concave and has a sharp ridge on 
either side at the ventro-lateral angles, broken into waves by equally acute 
but elongated nodes on the casts. Shells were not present. In old age 
these nodes: persist, but the ridges disappear and the venter becomes flat- 
tened, and finally convex. 
A cast from Denison, Tex, Duck Creek beds, United States Geolog- 
ical Survey, has very different sutures and is also somewhat different in 
general aspect. The living chamber is complete in the inner borders and 
is considerably less than one-fourth of a volution in length. It is in the 
gerontic stage; the inner tubercles are large, and the outer ones, terminating 
short, fold-like costee, are also very large. The venter is completely rounded 
and much zigzagged in correlation with the large tuberculose alternating 
folds and nodes of the coste. 
The whole diameter is 92 mm.; the outer volution, which is somewhat 
reduced by gerontic contraction, is 42 mm.; the umbilicus is 14 mm., this 
being enlarged in proportion to reduction of gerontic part of volution, and 
opposite from line of involution to venter is 36 mm. The saddles are quite 
distinct from those of specimens described above, but have the same distinctly 
phylliform aspect; the lobes are more alike and with similar serrations. There 
are nine saddles on the right side. The first lateral has the same deeply 
bifid form as in specimens of this species. The second to seventh have 
rounded leaf-like bases; the eighth is still phylliform, but broadens out and 
is bifid; the ninth is entire. The first lateral lobe is evidently very slightly 
divided, but the second to the fifth are more richly denticulated than the 
sixth and seventh and are faintly trifid (?); the eighth is perhaps entire, but 
not plainly seen. The living chamber is shorter in this specimen than in 
any other example of this species and the nodes are more like those of ser- 
pentinum, while the sutures agree better with those of subjectum. 
The principal distinction between this species and its allies of the same 
genus lies in the more elongated phylliform saddles and lobes. 
ENGONOCERAS GIBBosUM n. sp. Hyatt. 
Pl. XX, figs. 6-10; Pl. XXII, figs. 1-6. 
The best example of this species is an entire cast in my collection from 
Cook County, Tex. This has the median line of nodes along the central 
line of the lateral surface, the outer distinct and short and no perceptible 
