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, 3| inches. Proceedings Acad. Nat. Sciences, Dec., 1856, p. 312. 

 Locality. Santa Barbara, Gal. 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, Vahnc. 



Malea ringens, PI. V, fig. 22. 

 Dolium 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 Gatunensis, PL V, 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 ; but if they should be representatives of existing shells, they will 

 doubtless prove to be inhabitants of the Pacific coast, of the Isthmus, or of South America. 



CYTHEREA? Lam. 



Cythereaf (Meretrix) Dariena? PL V, fig. 21. Meretrix Dariena, Con. Desc. of FOBS, 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 yregaria, PL IV, fig. 18. Subquadrangular, elongated, longitudinally furrowed 



