72 
GEOLOGY-DESCRIPTION OF FOSSILS. 
depressed towards the apex ; ribs rather narrower than those of the opposite valve, obscurely 
bicarinated above, disk ornamented with close, fine, squamose, concentric wrinkles. Length, 4 
inches ; height, 3f inches.—Proceedings Acad. Nat. Sciences, Dec., 1856, p. 312. 
Locality. —Santa Barbara, Cal.—Dr. Newberry. 
OSTREA, Linn. 
Ostrea Titan , PI. IV, fig. 17, PI. V, fig. 17a, profile. Produced from beak to base, straight 
or slightly curved, substance very thick, coarsely laminated ; upper valve flat, very thick, 
somewhat gibbous ; lower valve profoundly ventricose, umbonated, the summit rising above 
the beak of the opposite valve. Length, .—Proceedings Acad. Nat. Sciences, 1855. 
Locality. —San Luis Obispo, California. 
FOSSILS OF GATUN, ISTHMUS OF DARIEN. 
MALEA, Valenc. 
Malea ringens , PL Y, fig. 22. 
Doliurn ringens, (Cassis,) Swainson. 
Locality. —Gatun. This shell inhabits the Pacific coast of South America, and the genus is 
unknown in the Atlantic. 
TURRITELLA, Lam. 
1. Turritella altilira, PI. V, fig. 19. Subulate, carinated; volutions with 2 distant, elevated, 
revolving, crenulated ribs, interstices with revolving lines ; body volution bicarinated at the 
angle. 
Locality.— Gatun.—Dr. Newberry. 
2. Turritella Ga-tunensis , PL Y, fig. 20. Subulate ; volutions each with 2 slightly concave 
spaces; body volution ventricose, much larger than the penultimate, having about 20 revolving 
lines, 7 or 8 of which are on the base, which is flattened ; 3 lines on the body volution larger 
than the others, the 2 lower ones remote. 
Locality. —Occurs with the preceding. 
TRITON, Lam. 
An imperfect cast of an unknown species occurs with the preceding. 
I have compared the above three univalves with what recent species and figures I have access 
to, and cannot identify them; hut if they should he representatives of existing shells, they will 
doubtless prove to he inhabitants of the Pacific coast, of the Isthmus, or of South America. 
CYTHEREA? Lam. 
Cytherea? {Meretrix) Dariena? PI. Y, fig. 21. Meretrix Dariena, Con. Desc. of Foss, and 
Shells collected in Cal., by Wm. P. Blake, p. 18. I have referred this shell to Cytherea, as it 
is probable that Venus meretrix may prove the type of a genus distinct from Cytherea. 
TAMIOSOMA, Conrad. 
An elongated tube, apparently entire, porous and cellular throughout its substance ; interior 
filled with numerous irregularly-disposed vaulted cells connected by longitudinal slender 
tubes, funnel-shaped beneath ; aperture resembling that of Balanus. 
Tamiosoma gregaria, PL IY, fig. 18. Subquad ran gular, elongated, longitudinally furrowed 
