GASTEROPODA. 
51 
Isonema depressa is described as being “ but little convex between the angular 
periphery and the imperforate umbilical regionand the striae below the 
periphery “ suddenly become obsolete.” 
The above features of genus and species are quite incompatible with the 
following forms. 
Callonema bellatula. 
PLATE XIV, FIGS. 10-15. 
Loxonema bellatula, Hall. Fourteenth Rep. N. Y. State Cab. Nat. Hist., p. 104. 1861. 
Isonema bellatula (H.) Meek. Proc. Acad. Nat. Sci. Phila., p. 252. 1865. 
“ “ “ “ Geol. Survey of Illinois, vol. 3, p. 443. 1868. 
“ “ “ H.-W. Twenty-seventh Rep. N. Y. State Mus. Nat. Hist., pi. 13, f. 12. 1875. 
“ “ “ Hall: Illustrations of Devonian Fossils: Gasteropoda, pi. 14. 1876 
Shell subovoid-conical; spire elevated and rapidly expanding below. Volu¬ 
tions about six or seven, the upper ones minute and somewhat gradually 
expanding to the third or fourth, and more rapidly below, the last 
one being very ventricose, regularly rounded or obtusely subangular 
towards the base. Aperture apparently transverse—its extension below 
not fully known; columellar lip thickened, spreading above and extended 
anteriorly. 
Surface marked by regular, even, sharply-elevated strife, with about equal 
interspaces, which are slightly turned backwards from the suture and 
gently curved to the base of the volution, and on the last one curving over 
the periphery with equal strength—a portion becoming obsolete, and 
others coalescing and becoming stronger as they enter the umbilical 
depression. 
The species presents the external characters shown in the figures 10-15 of 
plate 14, and I can find no means of separation between those showing an 
obtuse angularity at the base of the last volution and those which are regularly 
rounded and ventricose. The surface striae are alike in the several examples. 
In figure 10, which seems to me not to be specifically distinct from the 
others, the volutions are flattened upon the upper side for a narrow space 
