PTEROPODA. 
185 
ventral side of the specimen, and show on one part the continuous arching 
striae free from interruption by the fracture. This freedom from a longitudinal 
groove or interruption of the striae is still more completely shown in the 
specimens from the Falls of the Ohio, which are larger and usually better 
preserved than those of the Hamilton group in New York. 
Dr. Sandberger has included similar, but somewhat larger, forms under the 
genus Dentalium (D. annulatum and D. tcmiolcitum ), but the rigidly straight form 
and annulated surface of C. tenuicmdum are scarcely compatible with the typical 
forms of that genus, and it seems necessary therefore to adopt some other 
designation. 
COLEOLUS TENUICINCTUM. 
PLATE .XXXII, FIGS. 5-9 ; and PLATE XXXII A, FIGS. 6-10. 
Coleoprion tenuicinctum, Hall. Illustrations of Devonian Fossils: Pteropoda, pi. 27, figs. 1-4. 1876. 
Orthoceras, Yandell and Shumard. Geology of Kentucky, page 15. 1847. 
Shell an extremely elongate, gradually and regularly tapering cone, having 
in the largest individuals, a diameter of six millimetres at the larger 
extremity, with a length of seventy-five millimetres. 
Surface marked by fine closely arranged strife, or frequently with more distant 
oblique annulations, receding from the aperture, or sinuate on the ventral 
side—the degree of obliquity depending upon the position of the fossil, or 
the relation of the parts exposed to view. Interrupted longitudinal strife 
are visible in well preserved specimens. 
The individuals of this species are quite common in some localities of the 
Hamilton shales in the State of New York, but they are almost always in a 
crushed condition, and showing a line of fracture which may be mistaken for a 
longitudinal groove. The specimen originally figured is but slightly compressed, 
and the annulations are more distant than on any other one observed. 
The diameter and length of specimen's vary to a considerable degree, and 
no individual in the Hamilton shales has yet been found entire—the extreme 
apex being unknown. The specimens are usually rigidly straight, though 
sometimes curved towards the smaller end, as represented, probably occurring 
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