GASTROPODA. 941 
Raphistoma richmondensis.] 
RAPHISTOMA RICHMONDENSIS, ”. sp. (Ulrich. 
PLATE LXVIII, FIGS. 79. 
Shell 15 to 20 mm. in diameter, the spire almost flat, the hight between one- 
third and two-sevenths of the width; volutions four, very slightly convex on the 
upper side, 7. e. within the outer edge which forms a thin elevated rim; umbilicus 
very small in casts, apparently closed in shells. Surface striz fine and subequal on 
upper side, making the usual sigmoid curve, the change in curves occurring near 
the middle of the whorls. Just before reaching the peripheral rim the striz make 
another short backward turn. Beneath the periphery the striz are more unequal. 
At first they turn forward then more directly inward. 
This species resembles the Chazy FR. calyx Billings, but is smaller and relatively 
wider. In &. creviert, of the same author and formation, the edge is blunter, and 
the lines of growth curve more strongly forward beneath it. R. peracutum has an 
umbilicus and differs in several other respects. A very similar species, differing 
only in that it has a smal! umbilicus, occurs in the Stones River group in Tennessee. 
Formation and localityx—Richmond group, Richmond, Indiana. Good specimens rare. 
Collection.—H. O. Ulrich. 
Genus RAPHISTOMINA, n. gen. 
Faphistoma (part.) and Plewrotomaria (part.), of authors. 
For generic characters and general remarks see pages 932 and 934 to 939. 
As species of this genus are generally confounded with Raphistoma, it may be 
well to repeat the peculiarities upon which we base our separation. In Raphistoma 
the lines of growth on the lower side, which of course correspond with the outline 
of the lower lip, curve forward more or less strongly from from the peripheral edge. 
The outer half and more of the under lip therefore is convex, whereas in Raphistomina 
the corresponding portion is always concave. In species like Raphistomina laurentina 
Billings sp., this concavity is decided and extends over the whole anterior outline of 
lower lip. On the upper side of the whorls the striw curve backward again in 
Raphistoma just before reaching the peripheral edge. This, together with the 
forward curve immediately beneath the edge, produces a small notch in the outer 
angle of the aperture. In Raphistomina, on the contrary, there is no notch, the 
angle being either rectangular or turned slightly forward, in some cases forming a 
beak-like projection. Comparing the upper and lower lips we find that in Raphistoma 
their outlines do not correspond, the lower being more prominent and simply convex 
in the outer two-thirds where the upper forms a sigmoid curve. In Raphistomina, 
however, the anterior outlines of the two lips are either equal, or the lower is more 
