28 RATHBUN 
HYMENODORA FRONTALIS Rathbun. 
fHymenodora frontalis Rathbun, Proc. U. S. Nat. Mus., XXIv, 904, 1902. 
Integument very thin, but firmer than in ZH. glacialis; covered with 
fine wrinkles or rugose lines. Carapace and rostrum more than half as 
long as abdomen; median carina extending almost or quite to the mid- 
dle of the carapace, and advanced in a rostrum which is unusually long 
for the genus, being from two fifths to one half as long as the remainder 
of the carapace, and reaching the end or a little beyond the end of the 
antennular peduncle. The rostrum is a slender, sharp-pointed spine; 
distal half slightly curved upward and usually unarmed, basal half armed 

Fic. 8. Hymenodora frontalis. % (X about 2). Station 3308. 
with from 3 to 6 small spines above, two or three of which are beyond the 
line of the orbit. Occasionally there is a single spine on the distal half. 
Orbit deep; a tiny spine tips the suborbital lobe. Antennal spine strong ; 
from it a sharp carina runs back subparallel to the side margin quite to 
the posterior margin. Above this the branchial region bears a blunt 
ridge, chiefly longitudinal, but bent down at either end; a deep groove 
extends obliquely downward and backward from the orbital sinus nearly 
to the lower carina. 
The eyes reach to the middle of the basal segment of the antennule ; 
they are without pigment, and bear a slender, blunt spine close up to the 
cornea on the inner margin. The antennular peduncles are short, the 
segments diminishing successively in length; basal scale narrow-oval, as 
seen from above; upper flagellum very thick at base. Antennal scale 
lanceolate, outer margin nearly straight, tipped with a small spine; 
peduncle very stout, attaining the end of the first antennular segment. 
