GASTROPODA. 943 
Raphistomina denticulata.] 
The above description is based chiefly upon a number of silicified shells from 
Tennessee which we owe to the kindness of Prof. J. M. Safford. These differ, so far 
as we can see, from the Canadian types of the species only in having the upper side 
of the volutions a trifle more convex. L. lawrentina Billings sp., from the Calciferous 
of Canada, is closely related but is readily distinguished by the much deeper and 
wider sinus in the outline of its lower lip. 
Formation and locality—The original types are from the Black River limestone at Allumette island, 
in the Ottawa river, Canada. The Tennessee specimens come trom an equivalent horizon near Lebanon. 
If the species occurs in Minnesota it will probably be found in the Ctenodonta bed. 
RAPHISTOMINA DENTICULATA, ”. sp, (Ulrich.) 
PLATE LXVIII, FIGS. 21—23. 
This species is very closely allied to Fh. lapicida Salter, yet there should be little 
trouble in distinguishing good specimens. Carefully compared we find that in the 
new species the umbilicus is much narrower, the hight of the shell relatively 
greater, the sutures deeper because the edge of the whorls projects somewhat over 
the top of the succeeding volution, the aperture is a little more oblique and the 
periphery of the whorls less acute, Further, there is to be observed, especially on 
casts of the interior, an obscure ridge running parallel with but some distance 
beneath the peripheral carina. Finally, the peripheral edge is minutely toothed, a 
character that does not occur on the even better preserved examples of RP. lapicida 
seen by us. At present we know of no other species with which it need be 
compared. 
Formation and locality.—Top of the Black River group, Mercer county, Kentucky. 
Collection.—H. O. Ulrich. 
RaAPHISTOMINA MoDESTA, ”. sp. (Ulrich.) 
PLATE LXVIII. FIGS. 14—17. 
Differs from fh. lapicida, which it resembles more closely than any other known, 
in being smaller (12 to 15 mm. in diameter), in having a proportionally smaller 
umbilicus, and in its surface markings. On the upper side, which is also a little 
more depressed, the lines of growth are very faint, while the peripheral edge turns 
rather distinctly upward. On the- lower side the lines of growth are likewise 
obscure except in the peripheral half of the last whorl, where they appear as rather 
coarse undulations of which the best specimen has about seven in 5 mm. The 
course of the lines on this side, which of course corresponds with the outline of the 
lower lip, is more convex anteriorly than in R. lapicida. (Compare figs. 16 and 18 
on plate LXVIII). &. denticulata is a larger shell, has a higher spire and deeper 
sutures. 
