GASTEROPODA. ' 37 



iltonia and C. lirata ; being a little more ventricose than either, without the 

 flattened or concave band on the upper side of the volution. 



Formation and locality. In the coarse shales of the Hamilton group at Smyrna, 

 Chenango county, N. Y. 



Cyclonema Hamilton^. 



PLATE XII, FIGS. Jt-36. 



Cyrhmema Hamiltoniw, Hall. Descriptions of New Species of Fossils, etc., p. 19. 1861. 



" " Fifteenth Rep. N. Y. State Cab. Nat. Hist., p. 47, pi. 5, fig. 16 (not 15). 1862. 



" " " Illustrations of Devonian Fossils : Gasteropoda, pi. 12. 1876. 



Shell subglobose-conical ; height a little more than the width across the last 

 volution. Volutions four or five; apex minute and gradually expanding 

 to the body-whorl which is somewhat abruptly ventricose, flattened or a 

 little concave for a short distance below the suture, and the space limited 

 on the exterior side by a carina, which is the first of a series, marking the 

 periphery of the volution. 



Surface marked by extremely fine lamellose lines of growth, which are directed 

 backwards from the suture without bending or curvature in passing the 

 carinations. The volutions, except the narrow concave space above, are 

 marked by strong revolving elevated carinate lines, of which there are 

 from fourteen to eighteen on the body-whorl. These carinae are usually 

 simple and subequal, more or less distinctly defined, and sometimes alter- 

 nately stronger and more subdued, or with two finer ones between the 

 stronger. On each of the upper volutions there are three, four or five 

 of these carinse preserved, and they are distinctly crenulated by the 

  passage of the concentric striae, which are sometimes also bent forward 

 on approaching the first carination. 



This species has nearly the proportions of Pleurotomaria capillaria, except in 

 the more abrupt ventricosity of the body- volution. The flat or concave belt 

 on the upper side of the volution, which is without revolving striae and marked 



