4 [ 228 ] A. Wincliell on Fossils from the 
Ortiiis Barabuensis, n. sp. 
There are several imperfect specimens of an Orthis , apparently 
of the type of 0. b for at us. The form is transverse, with a 
straight hinge-line, and the sub-equal beaks a little elevated 
above it. Greatest width of shell along the hinge, in front of 
which the sides are considerably constricted, and continue to 
approach each other, though less rapidly, to the somewhat 
straight anterior margin. Ventral valve with a sinus of mode¬ 
rate depth, which is rather broad, and near flat at bottom. Sur¬ 
face with sixteen or eighteen ribs visible on the cast, the 
strongest of which limit the mesial sinus, which has in the 
middle a barely visible costal ridge. The interior of this valve 
exhibits a pair of rudimentary hinge teeth, separated bv a tri¬ 
angular foramen. The interior myary scars occupy only a 
small space near the beak, and present an elliptical outline. 
The dorsal valve is equally convex with the ventral, and ex¬ 
hibits a broad, depressed mesial fold. 
Length of hinge-line ’76 (100); length of shell from beak to 
anterior margin *38 (50). 
Dr. D. D. Owen ( Rep. Wis , Io, and Min., p. 575) and Shumard 
(St. Louis Trans., i, 627) have made allusion to the existence of 
this genus in the Potsdam sandstone of the northwest; and a 
species has just been described by Prof. Hall under the name of 
0. Pepina. Our specimens from Baraboo differ from both this 
and 0. Coloradoensis Shum., in its more transverse shape, fewer 
ribs and want of concentric lines, 
Straparollus (Ophileta) primordialis, n. sp. 
A planorboid shell, three-fourths of an inch in diameter, and 
having the apex of the spire depressed below the level of the 
outer whorl. The number of w r horls is probably about five, 
but only the last two are preserved in the best specimens. The 
tube enlarges very gradually, and is marked by a distinct carina 
just above the peripheral line, above and below which is a shal¬ 
low groove. 
Some of the specimens of this fossil greatly resemble the fig¬ 
ure of Ophileta complanataY anuxem, from the Calciferous sand- 
rock of New York; but the volutions enlarge a little more 
rapidly, and present a distinguishing angulation. No allied 
species has been described from the Potsdam sandstone (unless it 
be 0. compacta Billings, a description of which I have not seen). 
The Euomphalusf vaticinus Hall (16/A Rep. N. Y. Regents , p. 136) 
is described and figured as “gently convex above,” 
PlEUROTOMARIA ? ADVENA, n. Sp. 
A trochoid or sub-turreted shell, of at least four whorls, 
which are depressed-convex externally, and apparently destitute 
