GASTROPODA. 895 
Bucania nana.] 
its width somewhat greater than half the hight of shell; aperture slightly wider 
than high, subpentagonal. In a transverse section the volutions are semicircular in 
the dorsal half, with the umbilical slopes almost straight and the ventral side 
broadly indented by the preceding whorl: The width of the last volution expands 
from 6 mm, to 12 mm. in a specimen 18 mm. high. In the same specimen the slit 
has a length of 16.5 mm., and a width of about 0.7 mm. The slit-band is concave, 
bordered on each side by a delicate line, and crossed by numerous fine lunule. On 
each side of the slit and band the whole exposed surface is covered by a stroug and 
very sharply defined network, the deep meshes of which are so arranged that they 
form rows running in two directions, one almost directly across the volutions, the 
other obliquely forward and outward from the band. Finally, in certain lights, a 
third arrangement of the meshes will be observed, namely, in series passing 
obliquely forward from the sides to the slit-band. The last direction is approxi- 
mately at right angles to certain more or less distinct lines or varices of growth 
which interrupt the regularity of the network on old examples. (See figs. 43 
and 44), 
Excepting the surface markings, B. punctifrons agrees very well with the typical 
section of the genus. Even the retiform character of the sculpture is not entirely 
foreign to Bucania, since a kind of reticulation is frequently observed in the B. 
lindsleyi section that would not require a very great modification to produce ‘the 
ornamental sculpture of the species under consideration. Still, we have no suspicion 
that B. punctifrons is closely related to any of the B. lindsleyi section. For the 
present we consider it as a species standing entirely alone. 
Formation and locality.—Trenton group, at several localities in New York and Canada. The speci- 
mens upon which the above description is based were found in the lower part of the group (‘‘Orthis bed”) 
near Nashville, Tennessee, by Prof. Jas. M. Safford. 
Bucanta nana, n. sp. (Ulrich.) 
PLATE LXVI, FIGS. 41—44. 
Shell small, 10 mm. or less in“ hight, volutions two and a half or three, each 
embracing more than half of the preceding turn, expanding gradually and with 
moderate rapidity quite to the aperture, reniform in cross-section, broadly rounded 
on the dorsum and rather narrowly where the surface descends into the umbilicus; 
the latter is small, equalling only about one-fourth of the greatest diameter of the 
shell; aperture rounded when perfect, usually appearing more or less reniform, scarcely 
expanded, its width equalling about four-fifths of the hight of the shell; lips thin, 
the outer one with a central slit probably less than 2 mm. in length, the sinus also 
being unusually shallow, the inner lip prolonged slightly on each side and forming 
