,1 



description. When entire it must have looked like a gigantic Cyrtnliffs, and we 

 were at first inclined to place it in that genus. Closer investigation, however, 

 -.bowed that the -mface markings were in reality different and the shell too thick 

 for a Ci/rt"lil>-<. while in both respects it proved to correspond with some of the 

 Bucanin lindsleyi group of species. The curving transverse folds of the flattened 

 dor-al slope- are represented in other species of Hn<-<iniii by the salient edges of the 

 imbricating lamella-, 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 />'. 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 rhonil>oidal 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 toeott/y. Upper part of the Trenton group, DcKaltt county, Tennessee. 



Genus SALPINGOSTOMA, F. Roemer. 



Salpingotlonut, F. BOBMER, 1876, Lethe* Geognostica. 

 Baeania (pan. M M .1 . 1847, Pal. New York, TO). I. 



ropHon (part.), KM nw .M.l>. 

 Bueania (t TVemanofiu), WIUTKIKLD, 1882, Geol. of Wls., vol. Iv, p. I 



This genus will include a number of species that most American paleontologists 

 have considered as typical of the genus Bumnln. However, in discussing the latter 

 genus (see page 8S3) we have given our reasons for restricting its use to species con- 

 forming strictly with the type B. sul<-ntin<i, and for placing those of the type of Hall's 

 ilpinyostoina. It is therefore unnecessary to again take up this part 

 of the subject. 



I'ingostoma, 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 Burtini", 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 cln-ing of the long dor-al apertural -lit A 

 dorsal slit, equivalent to that of Salpin<j<t<miti. was present in the middle of the 



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