38 
BULLETIN OF THE LABORATORIES 
mens much less transverse and with distinctly alternate striae occur. 
In the free-stone this form occurs with var. cylindrica (= var. robusta, 
Hall), which latter, or a still more Orthis-like variety, occurs in 
congl. II. 
Orthis Vanuxemi, Hall, var. pulchellus, var. n. 
(Plate V, Fig. 9.) No. 1396. 
This beautiful little Orthis occurs in large numbers in a zone near 
the top or above the top of the quarry rock in Granville, and seems 
to pass into forms resembling those generally identified with O. mi- 
chelina. Without discussing the probable relationships of the two forms- 
we may simply notice the close resemblance of our specimens to those 
described by Prof. Hall, from ‘‘calcareous shales of the age of the 
Hamilton group” in several localities in Illinois, Mis^uri, Iowa, and 
New York. 
Shell nearly circular or sub-quadrate in outline, depressed, ven- 
tral valve generally longer than wide, most convex one-fifth from the 
beak, flattened, but not sinuous below. Hinge line short ; beak rather 
prominent, proLuding, acute; ears depressed, rounded. Surface cov- 
ered with numerous small, tubular striae which increase by bifurcation 
or more rarely implantation, sometimes by division into three, striae 
with perforations or oval punctures; surface also marked by concentric 
striae and more distant imbricating lines especially near the front mar- 
gins ; about three stria in the space of one millimeter. Foramen with 
cardinal process; interior of valve with large vascular impression, and 
mesial process. Dorsal valve nearly circular, convexity above the 
middle, cast with a broad mesial sulcus from the beak to near the mid- 
dle. Length of ventral valve 15 mm; width mm. 
Orthis michelina, var. burlingtonensis, H-, is hardly at all differ- 
ent. In it the perforations upon the striae are represented as elongate 
rather than circular, in which point our specimens agree. 
More typical specimens of O. michelina also occur in the free- 
stone. 
