MOLLUSCA. 449 



1886. Gryphcsa bryani Whitf., Pal. N. J., vol. i (Monog. U. S. 



G. S., vol. 9), p. 206, pi. 27, figs. 6-9. 

 1886. Ostrea glandiformis Whitf., Pal. N. J., vol. i (Monog. 



U. S. G. S., vol. 9), p. 205, pi. 27, figs. 1-5. 

 1905. Grypkaea bryani Johns., Proc. Acad. Nat. Sci. Phil, 



(1905), p. ii. 



Description. Shell oblique, more or less strongly extended 

 laterally to the left, looking upon the upper valve ; moderately 

 thick, more or less subtrigonal or subovate and exceedingly 

 irregular in outline. Lower valve strongly or moderately and 

 very irregularly convex, sometimes flattened or even concave to 

 beyond the middle o>f its length, attached or free, the scar of 

 attachment variable, usually small or of moderate size; surface 

 markings exceedingly irregular, consisting of concentric, more 

 or less squamose lines, which are often produced into irregularly 

 spinose processes near the hinge-line in those specimens which 

 have been strongly attached; surface also marked on many ex- 

 amples, by a few rather broad, irregular, radiating costse ; hinge- 

 area triangular, with a deep ligamental groove in the middle, 

 whose apex is deflected to the left. Upper valve flat, slightly 

 concave or slightly convex, sometimes convex towards the beak, 

 becoming concave towards the base, the surface marked by con- 

 centric squamose lines, the hinge area directed from 45 to 90 

 to the general plane of the valve. 



The dimensions of an average-sized, rather convex, lower valve 

 are: greatest length, obliquely from the beak to the postero- 

 basal margin, 42 mm.; greatest width at about right angles to 

 the last dimension, 28 mm.; convexity, 19 mm. 



Remarks. This is an exceedingly variable shell, and ap- 

 parently includes not only Ostrea bryani as described by Gabb, 

 and referred to the genus Gryphaea by Whitfield, but also 

 Gryphaea bryani var. precedent Whitf. and Ostrea glandiformis 

 Whitf. In a collection of one hundred or more individuals from 

 the typical locality for the species near Vincentown, specimens 

 can be selected to represent all three of these forms, with all 

 gradations between. Some of the larger and more convex speci- 



29 PAI, 



