GASTEROPODA. 45 



LOXONEMA HaMILTONIjE. 



PLATE Xin, FIGS. 15, 17. 



Loxonema nexilis, Phil. Hall : Geol. of N. Y. Surv. Fourth Geolog. Dist., p. 201. 1843. 



Not Loxonema nexilis of Phillips. Palaeozoic Fossils. 1841. 



Loxonema Hamiltonim, Hall. Descriptions of New Species of Fossils, etc., p. 25. 1861. 



" Fifteenth Rep. N. Y. State Cab. Nat. Hist., p. 53, pi. 4, f. 8. 1S62. 

 " "" " Illustrations of Devonian Fossils: Gasteropoda, pi. 13. 1876. 



Shell elongate, subulate. Volutions moderately convex, about thirteen in the 

 largest specimens known, very gradually increasing in size from the minute 

 apex, the last one ventricose. Aperture ovate, narrowing below; colu- 

 mella extended. 



Surface marked by longitudinal sharp, curving striae, which bend gently back- 

 ward from the suture, and forward towards the base of the volution, 

 having the greatest curve near the middle, those of the last volution 

 curving abruptly backward to the columellar lip. Striae separated by 

 distinctly defined grooves, which are a little wider than the ridges ; the 

 striae increasing in distance as the shell grows older. 



A single specimen, preserving thirteen volutions, measures less than one inch 

 and a half in length ; the diameter of the last volution is less than half an 

 inch. 



Specimens, imperfect at the apex, and having six or seven volutions, measure 

 about one inch and a quarter in length, with the diameter of the last volution 

 less tban half an inch. The striae on the upper part of the volution are not 

 unfruquently vertical or nearly so, and vary considerably in their degree of 

 curvature even in the same individual. 



This species is a common form in the Hamilton group, and differs from the 

 L. delphicola in the more numerous and more convex volutions, the more 

 strongly arched striae, the more extreme attenuation of the shell and less rapid 

 expansion towards the aperture. 



I have heretofore (Survey of Fourth Geological District) identified this species 

 with the Loxonema nexilis of Phillips ; but its form and proportions are inter- 



