242 
GAMMARTM. 
AMPBIPODA. GAMMARIDES. 
NAT ATOM A. 
Specific character. Last segment of the pereion, as well as the first 
four of the pi eon, dorsally carinated, and posteriorly elevated into a large 
tooth. Peduncle of the inferior antennae with the last two joints very long, 
and of equal length. 
Length \ inch. 
This species has the head produced anteriorly between 
the antennae into a small process; a similar but still 
smaller process projects upon the lateral margin, just in 
front of the eye, between the upper and lower antennae. 
The anterior segments of the body are smooth, but the 
sixth exhibits a rudimentary central dorsal tooth, which 
is increased to a considerable extent in the seventh seg- 
ment, at once distinguishing the present species from its 
congeners. As in D. spinosa , the four anterior segments 
of the tail are dorsally carinated, and posteriorly elevated 
into a tooth. The fourth segment is, moreover, distin- 
