﻿64 PROCEEDINGS OF THE NATIONAL 3MUSEUM vol. lOO 



about half the length of the valve. Both extremities broadly rounded, 

 the posterior end somewhat more broadly rounded than the anterior. 

 Highest well anterior to the middle. On the dorsal margin posterior 

 to the highest point there is a well-marked infolding. Dorsal margin 

 gently sloping from highest point to posterior rounded portion. 

 Ventral border almost flat with only a slight concavity at the mid- 

 point. On the anterior and posterior borders of both valves are 

 eight or nine very long heavy spines with blunted ends from which a 

 hair extends. Surface of valves covered with a series of rounded, 

 brownish spots. Left valve distinctly larger than the right on all 

 margins. First antennae with a long narrow terminal joint. Second 

 antennae with well-developed natatory setae which reach beyond the 

 tips of the terminal claws by about one-third the length of the setae. 

 Terminal claws heavy and toothed in their distal portion. First leg, 

 large with a long curved terminal claw. Subterminal segment 

 distinctly divided. Second leg with a curved beaklike terminal claw 

 and a long reflexed seta. Furca well developed and slightly curved. 

 Terminal seta about one-fourth the length of terminal claw. Sub- 

 terminal claw two-thirds the length of the terminal claw. Both 

 claws finely toothed on their distal portions. Dorsal seta heavy and 

 located about twice the width of the ramus from the base of the sub- 

 terminal claw. Length of dorsal seta slightly longer than that of the 

 subterminal claw and haired in its distal portion. Length 1.92 mm.; 

 height 1.05 mm. 



Male: Smaller than the female. Height about one-half the length, 

 highest in front of the middle, where the dorsal border forms a distinct 

 corner. From the highest point the dorsal margin slopes in an almost 

 straight line to the posterior end, where a more or less distinct angle 

 is formed. The two dorsal folds at about the middle of the dorsal 

 side are well marked. Ventral border almost flat with a slight con- 

 cavity. Anterior margin more rounded than posterior; both ends 

 heavily crenulated in addition to bearing spines as in the female. 

 Spines are not as numerous as in the female. Seminiferous tubules 

 very prominent and forming a dense whorl in the posterior part of the 

 shell. Length 1 .40 mm ; height 0.77 mm. (The considerable difference 

 in the size of the male and female taken in this collection leads to the 

 behef that the males were not fully matured. In Dr. Klie's specimens 

 there was only a slight disparity of size between the sexes.) 



Material examined. — Eleven mature specimens were collected by 

 Dr. Wright from Lagoa Precabura, near Mecejana, Cear^ (May). 

 One immature specimen was also found in a pool at Primavera, 28 

 kilometers west of Fortaleza (October) . 



Recorded distribution. — ^Acude Piaba in the state of Paraiba, Brazil 

 (Klie, 1939a). 



