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. t&niolaturn), but the rigidly straight form 

 and annulated surface of C. tenuicindum are scarcely compatible with the typical 

 forms of that genus, and it seems necessary therefore to adopt some other 

 designation. 



COLEOLUS TENCICINCTUM. 

 PLATE XXXII, KIGS. 5-9; and PLATE XXXII A, FIGS. 6 10. 



Coleoprinn tenuicinctum^ku.. Illustrations of Devonian Fossils: Pteropoda, pi. 27, figs. 1-4. 1876. 

 Orthoceras, Yasdkll and Shcmard. 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 striae, 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 striae 

 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 specimens 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 



24 



