334 
PALAEONTOLOGY OF NEW-YORK. 
Surface marked by fine undulating transverse striae, which are crossed 
by much finer obscure or obsolete longitudinal striae. 
This species differs from the preceding, in spreading less rapidly from the apex, 
and in being more gibbous on the back of the last volution, while it does not show 
the fine plications on the right side of the shell near the aperture. 
The specimen figure 6 a b has been referred with doubt to this species, but is 
probably distinct; and fig. 6 c, though having some of the features of this species, 
has been vertically compressed, which renders it more rotund : it probably belongs 
to the preceding. 
Fig 6 d. View of the aperture of a large specimen of this species. 
Fig. 6 e. A similar specimen, with less strongly plicated margins and a smaller spire. 
Fig. 6 f. The upper side of the spire of fig. 6 e. The specimen is not quite symmetrical in 
its convexity. 
Fig. 6 g. The upper side of the spire of the specimen fig. 6 d. 
Fig. 7 a. The lower side of a smaller specimen, showing strong plications. 
Geological position and locality. In the central portion of the Lower Helderberg 
group : Albany county. 
Platjceras sulcoplicatuiii (n. s.). 
Plate LIX. Fig. 7 b. 
Shell irregularly subhemispheric : apex posterior, minute, consisting of 
a single plain volution ; body volution abruptly expanding, ventricose: 
aperture somewhat quadrangular; peristome sinuate. 
Surface very strongly plicate ; plications four or five, sulcate, with one 
or two shallow grooves. 
This species is very peculiar in its broadly expanded last volution, which is more 
strongly plicated than any other species of the same size in this group of strata. 
The figure does not well represent the specimen. 
Fig. 7 b. The figure represents the specimen lying with the aperture downward. 
Geological positio?i and locality. In the central part of the shaly limestone of the 
Lower Helderberg group : Schoharie county. 
