90 PALEONTOLOGY OF NEW JERSEY. 
and shown its near relations to Piestochilus Meek. There is often some 
difficulty in distinguishing between the internal casts of Volutomorpha and 
those properly referable to Volutoderma. This latter genus appears to me 
to belong properly to the Volutide, as referred by the author, on account 
of the form, number, and position of the columellar plaits, and also on 
account of the form of the anterior portion of the shell itself. As stated 
under the remarks upon Peistochilus and Volutomorpha on p. 70, the shells 
of this latter genus are characterized by the narrow anterior canal and 
beak, by the very oblique columellar folds, and by the enlarged upper 
part of the volutions; while those of Volutoderma are characterized by the 
more yeutricose volutions, shorter spire, broader base, and short open canal, 
by having usually a larger number of less oblique and generally stronger 
columellar folds than in the other genus. The surface markings, so far as 
known from New Jersey specimens, are alike in the two genera. In many 
cases where imperfect examples of internal casts have to be examined of 
forms like Volutomorpha ponderosa, where the nearly equally tapering upper 
and lower parts of the specimen occur, with a broad anterior canal and 
very ventricose volutions, it is quite difficult to determine satisfactorily to 
which genus they belong, unless one can find evidence of the plications, 
for in this case the front of the shell has not been prolonged very much, 
and consequently seems to form a link between the two genera. On close 
inspection, however, it will be seen that the spire is more elongated even 
in this species than in any yet authentic form of Volutoderma. The follow- 
ing species I have placed under this latter genus. 
VOLUTODERMA BIPLICATA. 
Plate x; Higs) 1572: 
Volutilithes biplicata Gabb: Jour. Acad. Nat. Sci., Phila., 2d ser., vol. 4, p. 300, 
Pl. xuvil, Fig. 6; Synopsis, p. 93. 
Rostellites biplicata Meek, Check List Cret. and Jur. Foss., p. 21; Geol. N. J., 
Newark, 1868, p. 729. 
Volutoderma biplicata.Gabb: Proc. Acad. Nat. Sci., Phila., 1876, p. 292. 
Shell of medium size, robust, pyriform in outline, with a low spire and 
very large body volution; whorls three to four, ventricose, largest above 
