MARCELLUS SHALE. 
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3. Strophomena mucronata, n. s. — Shell semi-oval, with coarse striae, which radiate from 
an imaginary point beyond the beak; beak of the lower valve elevated ; hinge line extended 
into a kind of spine. 
This shell is readily distinguished by its coarse striae, which do not radiate from the beak, 
and the peculiar extension of the hinge line. 
Localities — Avon, Indian reservation, Erie county. 
4. Strophomenapustulosa, n. s. — Shell semi-oval, contracted beneath the hinge line ; sur¬ 
face covered with wrinkles and pustules, without striae ; hinge extremities angulated. 
The surface appears as if it may have been covered with spines, but I have not been so 
fortunate as to observe them. The shell when present is of a pearly hue, and readily sepa¬ 
rates, leaving a cast of the fossil. It is quite abundant. 
Locality — Avon, Livingston county. 
5. Avicula muricata, n. s. — Obliquely ovate; surface marked by elevated, radiating and 
concentric lines, giving a cancellated appearance ; from the junction of these lines rises a short 
spine; posterior wing small, produced into a short acute spine; anterior wing obtuse, with 
an oblique fold. 
The radiating lines are very faint on the posterior wing, and are not visible on the anterior 
wing. The small spines are usually broken off, except on the margin. This beautiful fossil 
will be readily identified from the figure. 
Locality — Avon. 
6. Avicula Icevis, n. s. — Obliquely ovate, with the hinge line slightly deflected on the ante¬ 
rior side ; beak convex, rather prominent; surface smooth, or marked with fine concentric lines 
of growth ; posterior wing triangular, abruptly acute, extending nearly in line with the margin 
of the shell; anterior wing obtuse, with a slight plication. 
This is a beautiful smooth shell, strongly contrasting in its surface with the last, both often 
being found together. 
Localities —Avon and Bloomfield. 
7. Avicula equilatera , n. s.— Obliquely semi-elliptical or sub-rhomboidal, nearly flat; hinge 
line straight, extending equally on each side of the beak; surface covered by radiating striae, 
which are,concentrically decussated by numerous elevated lines of growth. 
The wings are less distinctly marked than is usual in species of this genus, wdfich with the 
equilateral character readily distinguish it. The whole surface is regularly cancellated by the 
radiating striae and elevated lines of growth. 
Localities — Avon and Bloomfield. 
8. Orthis nucleus, n. s. — Hemispherical; lower valve very convex, with a depression or 
sinus from beak to base; upper valve flat, marked with concentric lines of growth, and fine 
striae ; hinge extremities rounded. 
