A NEW OSTRACOD FROM NANTUCKET. 
JOSEPH A. CUSHMAN. 
DuniNG the spring of 1905, several members of the Nan- 
tucket Maria Mitchell Association made collections from the 
various bodies of fresh water on the island. This material was 
kindly turned over to me for study. Among other noteworthy 
things is an ostracod of the genus Cyprinotus that is apparently 
new. Its description follows : — 
Cyprinotus americanus sp. nov. 
Plate 1, Figs. 1-8. 
Length of male 1.5 mm., width 0.7 mm., height 0.8 mm. 
The length of the shell is a little more than twice the width and the 
height is slightly greater than the width. The shell is thin, translucent, 
free from bands or color markings of any sort (Pl. 1, Fig. 1). 
Viewed from the side (Pl. 1, Fig. 1) the shellis suboval, with the greatest 
height slightly more towards the cephalic end. The dorsal margin is con- 
vex, the cephalic end much more convex than the caudal, which is almost 
bluntly pointed. The ventral margin is also slightly convex. 
Viewed from above (Pl. 1, Fig. 2) the shell is narrowly elliptical with the 
. anterior end more rounded than the posterior. 
` The third joint of the antenna is toothed on the distal part of each side, 
with one of the angles clothed with fairly long hairs. The single seta from 
this angle is doubly fringed. The last joint is short and bears two of the 
four terminal claws, these latter being finely toothed. The natatory sete 
extend to the end of the terminal claws. The characters of the antennules 
are shown in Fig. 4 (Pl. 1). The setz from the last joint are much shorter 
than those from the preceding ones. The characters of the mandible are 
very distinctive. The sete of the upper joint are peculiar, all of them 
being doubly fringed with scattered hairs. The large terminal setz are 
fringed on a single side. The third joint has many short spines on its ven- 
tral side. The jaw of the mandible has compound teeth of which the ante- 
rior ones are comb-like in structure. Lue 
The first foot has a long terminal claw the distal part of which is finely 
toothed. The fourth joint bears four short spines. The second joint has 
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