F. B. Meek—Descriptions of new Silurian Fossils, 279 
widens rapidly forward, though there is no defined revolving 
band at the angle. 
Length or height, 0.55 inch ; breadth about 0.50 inch. 
This shell possesses some of the characters of both Pleuro- 
fomaria and Scalites. In general appearance it is most like 
; se 
rapidly forward from, the angle of the volutions. Specifically, 
this shell is related to Plewrotomaria selecta of Billings, from 
Which it differs in having its strie of growth nearly obsolete, 
and in wanting the revolving angle just below the suture, seen 
in that species. on oe 
Locality and position. —Cincinnati group, at Cincinnati, Ohio. 
Mr. A. S. Miller’s collection. 
Genus Dicraniscus* M. 
Shell inequivalve, hinge line straight, rather long, hinge pro- 
vided with teeth and socket 
deltidium ; beak imperforate ; interior without dental or other 
aming, or processes of any kind; muscular impressions un- 
known. Ventral valve without a well developed area, but 
ee and on each side of the base of this with a prominent 
the hinge. Shell substance very thick about the hinge, and 
showing an im erfectly fibrous structure when broken, the fibers 
béing arranged at right angle to the surface of the valves. _ 
T have had specimens of this remarkable shell under consid- 
eration for nearly a year; but have been waiting for others to 
be found that would show its characters more clearly, all of 
those seen bein entary. Somewhat better specimens 
have recently been found by Prof. Orton, but none nearly en- 
re have yet been discovered. Those now at hand, however, 
* Dimin. of dixpavoc, a two pronged fork; in allusion to the long bifid cardinal 
