1874.] 249 [Eatbbun. 



specimens obtained, rendering the determination of the genus a little 

 doubtful. The posterior, end of the hinge seems to be marked with 

 the longitudinal teeth peculiar to Cucullea, while in the interior 

 moulds there is a slight, rounded depression, bordering the posterior 

 muscular imprint below, and extending some distance toward the 

 beak. As to shape the form is truly CucuUean. Size of a medium 

 specimens: length, 27 mm.; heiglit, 18 mm.; depth of both valves, 

 16 mm. 



Very abundant, as interior moulds, in the whitish limestone of- 

 the Ci;etaceous at Maria Farinha, Prov. of Pernambuco, Brazil.' 

 Dedicated to my teacher and fi-iend, Prof Ch. Fred. Hartt. 



CueuUea subcentralis sp. nov. 



Shell small, elongate, very gibbous, subrhomboidal in outline, and 

 about two-thiids to three-fourths as high as long. The anterior and 

 posterior margins are of nearly the same height, the latter being a 

 little the higher. The posterior margin is slightly oblique and 

 rounded, and curves abruptly to the ventral margin. The anterior 

 rounds gradually into the ventral, which curves but slightly, being a 

 little straightened along the middle, and is subparallel with the 

 hinge. The latter nearly equals the length of the shell, and joins the 

 anterior and posterior margins abruptly. 



The surface of the shell arches strongly from the beaks to tlie 

 ventral margin. Beaks situated just anterior to the middle ; from 

 them an undefined prominence or carina generally extends obliquely 

 across the intei'ior mould of the shell to the lower posterior angle. 

 This marks the beginning of the posterior slope which is very ab- 

 rupt. A shallow rounded depression runs parallel to the prominence, 

 and above it, on the posterior slope ; but these features are not al- 

 ways apparent. The valves are most convex in the upper part, in 

 the umbonal region and along the carina, and the whole upper part 

 of the shell is usually very much inflated. 



In the interior moulds the beak is. quite pointed and incurves 

 about half way to the hinge, above which it is moderately elevated. 

 Its inclination forward is not very strong. A shallow, rounded de- 

 pression, very narrow where it begins, but broadening out and shal- 

 lowing as it advances, extends a little obliquely backward from the 

 apex of the beak toward the ventral margin. Near the margin it has 

 disappeared. In the various specimens it is differently developed, 

 sometimes extending but a little way from the beak. This must indi- 

 cate a corresponding prominence in the interior of the valves. The 



