GASTROPODA. 897 
Salpingostoma.] 
description. When entire it must have looked like a gigantic Cyrtolites, and we 
were at first inclined to place it in that genus. Closer investigation, however, 
showed that the surface markings were in reality different and the shell too thick 
for a Cyrtolites, while in both respects it proved to correspond with some of the 
Bucania lindsleyi group of species. The curving transverse folds of the flattened 
dorsal slopes are represented in other species of Bucania by the salient edges of the 
imbricating lamelle, while the fine obliquely revolving lines in the depressed 
interspaces are commonly present in the genus. The volutions expand very rapidly, 
and in this particular, as well as in the dorsal angulations, the species corresponds 
perhaps best with B. nashvillensis, figured on the same plate. A view of the aperture 
of the specimen therefore agrees rather closely, in its lower part, with figure 37 of 
the plate. But the umbilicus is larger and much more sharply defined than in that 
species, the sides of the volutions being compressed into knotted keels. These 
lateral keels are nearly central on the inner whorls in a side view, but as growth 
proceeded its position became more ventral, the umbilical slope becoming at the 
same time more abrupt. For the same reason the transverse section of the whorls 
changes from rhomboidal to triangular. Only a small portion of the slit-band 
remains. This is slightly elevated and flat. Seven or eight of the revolving lines, 
which as usual are irregularly wrinkled, occur in 4 mm. 
Formation and locality.—Upper part of the Trenton group, DeKalb county, Tennessee. 
Genus SALPINGOSTOMA, F. Roemer. 
Salpingostoma, FE. ROEMER, 1876, Lethzea Geognostica. 
Bucania (part.), HALL, 1847, Pal. New York, vol. i. 
Bellerophon (part.), ExcHwALD. 
Bucanta (?Tremanotus), WHITFIELD, 1882, Geol. of Wis., vol. iv, p. 224. 
This genus will include a number of species that most American paleontologists 
have considered as typical of the genus Bucania. However, in discussing the latter 
genus (see page 883) we have given our reasons for restricting its use to species con- 
forming strictly with the type B, sulcatina, and for placing those of the type of Hall’s 
B. expansa in Salpingostoma. It is therefore unnecessary to again take up this part 
of the subject. 
Salpingostoma, as understood by us, will include shells whose inner volutions 
correspond in nearly every respect with the whole shell of the most typical species 
of Bucania, and it is only in fully grown entire examples that the peculiarities of the 
genus are apparent. These consist in the abrupt development of a thick and greatly 
expanded aperture and in the anterior closing of the long dorsal apertural slit. A 
dorsal slit, equivalent to that of Salpingostoma, was present in the middle of the 
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