372 
PALAEONTOLOGY OF NEW YORE. 
attenuation toward the apex in this length. Smaller fragments have been 
noticed, having an apical angle near the apex but little larger than the 
above. 
This species resembles C. eugenium, and is distinguished by the greater cur¬ 
vature of the tube, smaller apical angle, less regular and prominent transverse 
expansions. In C. citum the curvature of the tube is somewhat greater, and 
the transverse folds are finely plicated. 
Formation and localities. In the Schoharie grit, at Schoharie, N. Y., and from 
the crystalline sandstone of the Upper Helderberg group, at Pendleton, Ind. 
Cyrtoceras citum, n. sp. 
PLATE LI, FIGS. 1-3, AND SUPPLEMENT. 
Shell slender, arcuate, making about one-lialf of one volution, and showing 
some variation in the amount of curvature in different individuals. Trans¬ 
verse section circular. Tube regularly and gradually enlarging from the 
apex to the aperture. Apical angle 11°. 
The extent of the chamber of habitation has not been fully observed. 
The crenulations are well preserved over the internal mould of the tube as 
regular, rounded, longitudinal ridges and intermediate striae. The ridges are 
continuous, and form nodes on the transverse annulations of the internal 
mould. Aperture entire, with the exception of a distinct sinus in the ven¬ 
tral margin, corresponding to the sinus in the ornaments of the test. 
The depth of the air-chambers has not been determined. Septa smooth, 
moderately concave. 
Siphuncle close to the ventral side; its elements unknown. 
Test thin, having a thickness of .75 mm. Surface marked by lamellose 
lines of growth. Tube ornamented with regular, numerous, sharp, trans¬ 
verse, foliate, plicate expansions of the test, which have an elevation of three 
mm. above the general surface. There are about five of these plicae in the 
length of ten mm. Toward the apex they become more numerous and less 
prominent. Sinus well marked. 
