GASTROPODA. 873 
Protowarthia subcompressa.] 
doubt of the correctness of our identification, nor of the specific identity of a large 
proportion of the specimens that American authors generally and erroneously place 
under Sowerby’s Bellerophon bilobatus and P. cancellata. The only difference between 
the two supposed species mentioned by Hall is that one has a cancellated surface, 
the other not. According to our view this difference is merely a matter of preserva- 
tion, and if we are correct in this then P. cancellata is the commonest by far of all 
the Lower Silurian bellerophontids. 
As to P. bilobata Sowerby, the original figures of which are reproduced on page 
869, we have not the least doubt that it is specifically distinct from P. cancellata, 
that species being a larger and more globose form. Indeed, we doubt very much 
that Sowerby’s species occurs in America. 
Formation and locality. —Not uncommon in the Black River group, principally in the Ctenodonta 
bed, at Minneapolis, St. Paul, Cannon Falls, Chatfield and other localities in Minnesota. Also in Mercer 
county, Kentucky, and in Canada. It is very abundant in the Trenton, Utica, Loraine, and Richmond 
groups, in the first three especially, at numerous localities in Minnesota, Wisconsin, Iowa, Illinois, Ken- 
tucky, Ohio, Indiana, Tennessee, New York and Canada. 
PROTOWARTHIA SUBCOMPRESSA, 2”. sp. (Ulrich.) 
PLATE LXIII, FIGS. 40—44. 
Shell large, compressed-subglobose, the greatest hight and width about as six . 
is to four; back broadly rounded, sides somewhat flattened, umbilicus closed, 
wanting; aperture semi-ovate, outer lip thin, inner lip moderately thick and reflexed 
in the umbilical regions; callosity extending over the whole front of the inner 
volution, apparently smooth; sinus broad and about as deep, the depth decreasing 
slightly with age; apertural lobes rounding very gently to the sinus where the 
outline makes a rather sharp curve. Surface marked by fine lines of growth and 
near the aperture by some obscure wrinkles. The callosity which extends over the 
inner volutions exhibits the usual fine irregular revolving lines in the umbilical 
regions. When the shell is removed, the cast shows a narrow furrow down the 
center of the back and several more faintly on each side. Greatest diameter 41 
mm.; smallest diameter 29 mm.; width of aperture 27.5 mm.; hight of same (central) 
19.5 mm.; width of inner volution 13 mm.; depth of sinus 7 or 8 mm. 
This fine species, besides attaining a greater size than P. cancellata, differs from 
it in being narrower and in wanting, as far as known, the delicate revolving lines 
of that species. The umbilical callosity of the inner lip is also less and does not 
slope outwardly, the edge only being reflected. Bellerophon morrowensis Miller and 
Dyer, which also may belong to Protowarthia, is insufficiently known. According to 
the descriptions, it seems to differ in having the dorsal side sharply angular. P. 
planodorsata has a wider aperture, revolving lines, and a flat dorsum. 
