28 



RATHBUN 



HYMENODORA FRONTALIS Rathbun. 

 Hymenodora frontalis Rathbun, Proc. U. S. Nat. Mus., xxiv, 904, 1902. 



Integument very thin, but firmer than in H. 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 



FIG. 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 antennulae ; 

 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. 



