480 MARGUERITE HENRY. 
Genus CHYDORUS Baird. 
CHYDORUS DENTICULATUS sp. nN. 
(Plate XLII, figs. 15, 16.) 
The length of this form reaches “46mm. The shape is 
sub-globular; seen laterally, the dorsal margin of the cara- 
pace is strongly arched, forming a very obtuse angle with 
the posterior edges, the ventral edges of the valves are 
curved anteriorly straight for the greater part of their 
length, also forming an obtuse angle with the posterior 
edges, the latter are slightly curved. 
The head is small; the dorsal margin forms an even curve 
with that of the carapace, the rostrum is long and narrow 
slightly recurved, appressed to the trunk. The eye is of 
moderate size; the ocellus is smaller, rounded in shape and 
situated twice as far from the end of the rostrum as from 
the eye. 
The surface of the carapace is marked by small pits which 
are larger and more conspicuous in the dorsal part, a few 
striations present in the antero-ventral portion. The 
ventral edges of the carapace are beset with feathery hairs. 
and the anterior half has in addition a row of small denticles. 
The antennules are small and reach less than half the 
length of the rostrum. 
The tail-piece (fig. 16) is strongly built; behind the anal 
prominence the dorsal edge is a pronounced S-shape; there 
isa very distinct supra-anal angle. There are about fifteen 
groups of spines present on the infra-anal margin. The 
end-claws are long, and have one long and one short 
accessory denticle at the base of each. 
Two summer eggs are present in the brood-pouch. 
Specific Characters.—Shape sub-globular; dorsal margin 
of the carapace arched, ventral curved anteriorly and 
posteriorly straight in the middle, narrow posterior edges. 
