GASTEROPODA. 
45 
Loxonema Hamiltoni^. 
PLATE XIII, FIGS. 15, 17. 
Loxonema nexilis, Phil. Hall: Geol. of N. Y. Saw. Fourth Geolog. Dist., p. 201. 1843. 
Not Loxonema nexilis of Phillips. Palaeozoic Fossils. 1841. 
Loxonema Hamiltoniee, Hall. Descriptions of New Species of Fossils, etc., p. 25. 1861. 
“ “ “ Fifteenth Rep. N. Y. State Cah. Nat. Hist., p. 53, pi. 4, f. 8. 1862. 
“ “ “ 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 than half an inch. The striae on the upper part of the volution are not 
unfreqtiently 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 strise, 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- 
