264 
GEOLOGY OF THE FOURTH DISTRICT. 
2. Avicula acanthoptera, n. s. — Obliquely ovate, with a small acute anterior wing; the 
posterior wing ending in an acute spine, which extends as far as a line parallel with the pos¬ 
terior margin of the shell. Locality, Phillipsburgh. 
The following forms are found in the green and olive shales and shaly sandstones of Rock¬ 
ville and Phillipsburgh on the Genesee, and they are the prevailing fossils. They are all 
entirely distinct in form, and in the style of marking upon the surface. 
119. 
1. Pterinea? suborbicularis. 4. Pecten cancellatus. 7. Pecten? striatus. 10. Limaglaber. 
2. Pecten duplicatus. 5. Avicula? signata. 8. Pecten? crenulatus. 11. Lima obsoleta. 
3. Lima rugaestriata. 6. Pecten ? convexus. 9. Pecten ? dolabriformis. 
1. Pterinea? suborbicularis, n. s.— Suborbicular, or broadly semi-elliptical; surface 
marked by numerous, somewhat undulating ribs, which alternate with smaller ones toward the 
margin ; ribs crossed by concentric wrinkles, producing a rugose surface ; wings scarcely 
distinct; hinge line angulated at the extremities. 
Locality —Hobbieville, Allegany county. 
2. Pecten duplicatus, n. s.— Ovate-orbicular, equilateral, convex above ; ears small, nearly 
equal; surface marked by numerous radiating ribs, which are plain above, and equally can¬ 
cellated by concentric lines, but becoming uniformly duplicate and rugose toward the base. 
This fossil is readily distinguished by its great breadth and the duplicate rugose striae. It 
bears some resemblance to P. plicata, Sowerby. 
Locality —Phillipsburgh, Allegany county. 
3. Lima rugaestriata, n. s. — Oblong, obliquely ovate, moderately convex; ears small, not 
very distinct from the shell; surface with strong radiating striae, which augment toward the 
base, and are crossed by elevated undulating lamellae, giving the surface a rugose appearance, 
which is visible in the enlarged portion. 
Localities —Rockville ; Hobbieville, Allegany county. 
