528 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.49. 



Hinge line slightly arched and not making a sharp angle with the 

 anterior and posterior margins. Sinulus small but very prominent 

 and almost an equilateral triangle. 



The type, Cat. No. 273688, U.S.N.M., is a single valve, probably 

 nearly adult, from Ceara, Brazil, and measures: Length, 66 mm.; 

 breadth, 38 mm.; diameter, if both valves were present, would be 

 24 mm. There is also a younger specimen, whch measures : Length, 

 39 mm.; breadth, 22 mm.; diameter, 14 mm. 



This species shows no close relationship to any described species. 

 Its nearest relative is Anodontites wymani Lea, but the two species 

 differ in form, color of periostracum and nacre, and especially in the 

 color of the prismatic margin. The sinulus of wymani is long and 

 narrow, while that of salmonea is nearly an equilateral triangle. The 

 hinge plate of wymani is short, broad, and heavy; that of salmonea 

 is longer, narrower, and Ughter. 



ANODONTITES DAROCHAI, new species. 



Plate 68. 



Shell very thin and fragde, somewhat inflated, regularly rounded 

 in front and angulately rounded behmd, somewhat constricted just 

 in front of the middle. Widest near the posterior end of the hinge 

 line. Beak eroded, upper portion of each valve with numerous, 

 obscure, evenly spaced, channeled lines. Periostracum thin, smooth, 

 polished, greenish olive, with the rest periods indicated by a brownish 

 line. Posterior ridge evenly rounded. Posterior dorsal area dark 

 green with two darker green rays. Many other green rays over the 

 entire surface which are widest and darkest posteriorly, while an- 

 teriorly they are narrow and faint. 



Nacre highly iridescent, suffused with a lurid cast, marked by 

 fine radiating lines in the texture of the shell. Channeled concentric 

 lines of the outer surface showing through. Hinge line straight, 

 making abrupt angles with the anterior and posterior margins. 

 Cavity of the beaks and vicinity of the sinulus diseased, and this 

 disease obscures the character of the sinulus. 



The type. Cat. No. 273687, U.S.N.M., is a single valve from Ceara, 

 Brazil. It is not yet fully adult. It measures: Length, 75 mm.; 

 breadth, 45 mm.; diameter, if both valves were present, would be 

 24 mm. 



It is named in honor of the donor, Mr. Dias da Rocha. 



A young specimen from the same place sent by Mr. da Rocha 

 possibly belongs to this species, but has a bluish nacre and a light 

 greenish periostracum. Anodontites sinuosus is the nearest relative 

 of this species. The former is nearly truncate posteriorly, while the 

 latter is somewhat nasute, and the two species differ in other respects, 

 but it is possible that a large series of specimens would show A. 

 darochai to be a variety of A. sinuosus. 



