GASTROPODA. 925 
Bucanopsis carinifera.] 
BUCANOPSIS CARINIFERA, 2. sp. ( Ulrich.) 
PLATE LXII, FIGS, 56—61. 
Shell less than medium size, the hight varying in thirty-five specimens between 
7 mm, and 15 mm.; width of aperture nearly or quite equal to the hight. Volutions 
two or two and one-half, rather closely coiled, embracing to a little more than one- 
half, with a strong, prominent, flat-topped dorsal keel, from which the surface 
descends in a wide concave slope; sides rounding somewhat narrowly into the small 
open umbilicus; section of volutions broadly cordate. Aperture broad, somewhat 
triangular-ovate in outline; outer lip thin, with a moderately deep V-shaped central 
emargination; inner lip thick, very wide, reflected laterally, extending downward 
over the preceding volution whose keel shows through very distinctly. Surface 
with fine straight revolving strie, alternating somewhat in strength; transverse or 
growth lines, excepting an occasional wrinkle, usually very faint, but on the larger 
specimens they become much stronger and incline to be irregular. Slit-band 
flat, smooth so far as known. 
This, the type and only known Lower Silurian representative of the proposed 
genus Bucanopsis, reminds one somewhat of the Kuropean B. substriatus Krauss, but 
the dorsal carina is much more prominent and the slit-band narrower than in that 
rather doubtful Upper Silurian species. None of the Gotland species of the genus 
have the dorsum carinated. Of Lower Silurian Bellerophontide, Bellerophon troosti 
and B. platystoma are somewhat similar, but as the former has more rounded 
volutions and the latter quite a differently shaped aperture, there is little likelihood 
of confusion between them even as casts. Being true bellerophons they have of 
course no revolving lines, while the carina is never so prominent as in Bucanopsis 
carinifera. 
We have about fifty specimens of what we take to be the same species from the 
Loraine group at Cincinnati, Ohio. They are, however, smaller than the Trenton 
form, the hight being in most cases less than 7 mm. and in only one as much as 10 
mm. Not one of them exhibits even a trace of surface markings although preserv- 
ing the shell, or rather a replacement of the same in crystalline calcite. But the 
absence of surface markings on these specimens should not be considered as proof 
that they were originally without them, since they are wanting also on all the other 
Gastropoda occurring in association with them. Among these other forms are well 
known species of Lophospira and Cyrtolites ornatus, the surfaces of which under more 
favorable conditions are always distinctly sculptured. 
Formation and locality.—Upper part of Trenton group, near Danville, Kentucky; Loraine group of 
the Cincinnati period, Cincinnati, Ohio. 
Collection.—E. O. Ulrich. 
