70 GEOLOGY DESCRIPTION OF FOSSILS. 



regularly and profoundly rounded ; umbonal slope abruptly rounded ; summit prominent, pos 

 terior to the 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 Montereyana, 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 ] inches. Proceedings Acad. Nat. Sciences, Dec., 1856, p. 313. 



Locality. Monterey, Gal. 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? sulsinuata, 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, Sowerby. 



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. 



AR.CA, Lin. 



1. Area canalis, PI. II, fig. 8. Subtrapezoidal, 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- 



