70 
GEOLOGY—DESCRIPTION OF FOSSILS. 
regularly and profoundly rounded ; umbonal slope abruptly rounded ; summit prominent, pos¬ 
terior to tbe middle of the valve ; anterior extremity angular. Length 1 inch.—Proceedings 
Acad. Nat. Sciences, Dec., 1856, p. 313. 
Locality .—Monterey county, California.—Dr. Newberry. 
MYA, Lin. 
Mya Monterey ana, PI. II, fig. 4. Suboval, slightly ventricose, thin, inequilateral; summit 
hardly prominent; anterior end subtruncated? posterior end acutely rounded, the extremity 
situated more nearly on a line with the beak than the base ; disk concentrically rugoso-striate. 
Length 1^ inches.—Proceedings Acad. Nat. Sciences, Dec., 1856, p. 313. 
Locality. —Monterey, Cal.—Dr. Newberry. 
This and the preceding fossil belong to the same rock in which the Schizopyga occurs, the 
group having no resemblance to that of Estrella, or other localities referred to in this paper. 
Mya ? subsinuata, PI. II, fig. 5. Somewhat sinuous, ovate, slightly reflected at both ends; 
contracted medially or from beak to base. 
Locality. —Monterey county. 
ARCOPAGIA, Leach. 
Arcopagia medialis, PI. II, fig. 6. Oval, both valves slightly ventricose anteriorly ; upper 
valve much contracted or concave towards the umbonal slope, which is angulated ; post umbonal 
slope slightly contracted in the middle, emarginate at base ; the corresponding slope of the lower 
valve deeply folded, reflected towards the extremity ; disks rugoso-striate concentrically.—Pro¬ 
ceedings Acad. Nat. Sciences, Dec., 1856, p. 314. 
Locality. —Monterey county, Cal.—A. S. Taylor. 
This shell is proportionally longer than A. biplicata, Conrad, of the Maryland Miocene, but 
the general resemblance is noticeable and adds to the probability that the very remote strata in 
which they occur are parallel. 
TAPES, Sowerly. 
Tapes linteatum , PI. II, fig. 7. Oblong-oval, ventricose; buccal side short, extremity 
obtusely rounded ; anal side elongated, end regularly rounded ; ligament margin long, oblique, 
straight; disks radiated with fine, unequal lines, except on the post-umbonal slope, which is 
entire.—Proceedings Acad. Nat. Sciences, Dec., 1856, p. 314. 
Locality. —California.—Dr. Newberry. 
ARC A, Lin. 
1. Area canalis , Pl. II, fig. 8. Sub trapezoidal, ventricose ; ribs 24 to 26, flattened, scarcely 
prominent, divided by a longitudinal furrow ; disk concentrically wrinkled ; umbo ventricose ; 
summits prominent, remote from the centre.—Proceedings Acad. Nat. Sciences, Dec., 1856, p. 314. 
Locality. —Santa Barbara, Cal.—Dr. Newberry. 
2. Area trilineata, PI. II, fig. 9. Trapezoidal, somewhat produced, inequilateral, ventricose; 
ribs 22-24, scarcely prominent, square, wider than the intervening spaces, ornamented with 
three impressed or four raised lines ; disks concentrically wrinkled; summits prominent ; beaks 
approximate. Length 3 inches.—Proceedings Acad. Nat. Sciences, Dec. 1856, p. 314. 
Locality. —Occurs with the preceding. 
3. Area congesta, PI. II, fig. 10. Rhomboidal, ventricose, inequilateral; ribs about 27, con- 
