FAUNA OF ORTHAULAX PUGNAX ZONE. 123 



Family OSTREIDAE. 



Genus OSTREA (Linnaeus) Lamarck. 



Ostrea Linnaeus, Syst. Nat., ed. 10, p. 696, 1758.— Lamarck, Prodrome, 

 p. 81, 1799. Type, Ostrea cilulis Linnaeus. 



OSTREA SELLAEFORMIS Conrad var. RUGIFERA Dall. 



Ostrea seUaeformis Conrad var. rtigifera Dall, Trans. Wagner Inst, vol. 3, 

 pt. 4, p. 678, 1898. 



Oligocene of the Tampa silex beds, Ballast Point; of the Chipola 

 marls and the lower bed at Alum Bluff, Chattahoochee River, Flor- 

 ida. U. S. Nat. Mus. No. 114825. 



The typical 0. seUaeformis, as is well known, is Eocene in distribu- 

 tion ; the middle Oligocene form is that I have called rugifera, but 

 which is not yet represented by any really well-preserved specimens 

 in the material I have seen ; the last term of the series in the upper 

 Oligocene, at Oak Grove, Santa Eosa County, Florida, is that to 

 which I have given the name of variety paucipUcata. 



OSTREA MAURICIENSIS Gabb? 



Ostrea mauriciensis Gabb, (part) Jonrn. Acad. Nat. Sci. Phila., ser. 2, p. 



376, pi. 67, 1860. 



Oligocene of the mixed marls of southern New Jersey, of the 



layers above the Altamaha grit of Georgia, and of the Tampa silex 



beds at Ballast Point, Tampa Bay, Florida. U. S. Nat. Mus. No. 



153851. 



Part of Gabb's 0. mauriciensis seems to be young 0. georgiana 

 Conrad; part approaches very closely the 0. virginica Gmelin; but 

 in nearly all cases the superficial layers of the shell have been de- 

 stroyed, and the specific identifications must be merely guesswork. 

 AVhether there is a really distinct species in the complex remams 

 uncertain. 



OSTREA VAUGHANI, new species. 



Plate 19, fig. 6. 



Shell solid, heavy, with the external sculpture of both valves simi- 

 lar, composed of closely adjacent concentric imbrications or over- 

 lapping lamellae corresponding to the incremental Imes, with no 

 trace of any radial sculpture; upper valve moderately convex; beak 

 strongly recurved, with a deep wide medial ligamentary sulcus; the 

 inner margins of the valves near the hinge, with a sparse denticula- 

 tion, especially on the anterior margin. Length 120, width 85, depth 

 of paired valves 60 mm. 



Ballast Point, Tampa Bay, either from the silex beds or the lime- 

 stone immediately above them; E. J. Post. U. S. Nat. Mus. No. 

 166092. 



