448 CRETACEOUS PALEONTOLOGY. 



Description.. — Shell of medium size, laterally arcuate. The 

 dimensions of a rather small individual are: length along the 

 median line from beak to posterior extremity, 45 mm. ; distance 

 between beak and posterior extremity, 2 1 mm. ; width of shell 

 at middle, 17 mm.; length of hinge-line, 12 mm. Shell more or 

 less strongly auriculate, the auriculations variable in size. Hinge- 

 line straight. Shell surface marked by from four to seven pro- 

 found and broad plications along the lower or convex margin, 

 which rapidly die out, leaving the central area of the shell non- 

 plicate; the upper or concave margin marked by much smaller, 

 short, marginal plications or denticulations. Lower valve mod- 

 erately convex, with a small scar of attachment ; upper valve flat. 

 Entire surface O'f both valves marked by fine, more or less 

 irregular, concentric lines of growth. 



Remarks. — This species is a close ally of 0. mesenterica. The 

 two species agree in having the median portion of the shell non- 

 plicate, but 0. nasida is a much larger and coarser shell, with 

 broader and more profound plications. It should, perhaps, be 

 considered only as a varietal form of O. fnesenterica, but it is for 

 the most part characteristic in New Jersey, of higher beds than 

 the Navesink marl, where that species is most abundant. The two 

 forms usually do not occur in association, and it is at least con- 

 venient to have a special name for the designation of this form. 



Formation and locality. — Navesink marl, near Red Bank 

 (120) ; Red Bank Sand, Red Bank (116, 123), near Middletown 

 (112); Tinton beds. Beers Hill cut, south of Keyport (129^), 

 near Freehold (132), near Red Valley (123). 



Geographic distribution. — New Jersey, Texas. 



Ostrea bryani Gabb. 

 Plate XLIV., Pigs. 1-5. 



1876. Ostrea bryani Gabb, Proc. Acad. Nat. Sci. Phil. (1876), 



p. 321. 

 1884. Ostrea bryani White, 4th Ann. Rep. U. S. G. S., p. 293. 

 1886. Gryphcea bryam var. precedent Whitf., Pal. N. J., vol. i 



(Monog. U. S. G. S., vol. 9), p. 194, pi. 26, figs. 7-8. 



