202 STALK-EYED CRUSTACEA 
The branchial formula is as follows: — 
Somites Villy Slee, — 1B xe xalp dO Slit | OHV 
Pleurobranchie 0 1 i a 1 1 r 1= 6417 
Arthrobranchia 1 1 2 2 2 2 2 012 
Podobranchize 0 sl 1 1 il 1 0 O= 5 
Epipods 1 1 1 1 al 1 0 0= (6) 
23+17+(6) 
With the exception of those on the tenth and fourteenth somites the 
pleurobranchiz are very small and might be called rudimentary if it were 
not for the plumose structure of all but the one on the thirteenth somite. 
The podobranchix decrease in size posteriorly until, on the antepenultimate 
pair of legs, they are reduced to small and weak organs. 
‘Tf the branchial formula of Hemipeneus be compared with that of Aristeus 
(page 195), it will be seen that they are very nearly alike; the difference 
consisting in the further reduction in size of the pleurobranchiz in the 
latter genus, and the complete disappearance of the podobranchia of the 
twelfth somite, which is very small, be it observed, in Henupeneus. In its 
facies Henipeneus differs considerably from Aristeus. It has a slenderer body, 
flattened eye-stalks, longer antennular peduncles and antennal scales, peculi- 
arly long-fingered chela and flattened meri on the chelipeds, and long, 
exceedingly slender, styliform ultimate and penultimate thoracic appendages. 
The largest specimen of this species, —a female from Station 3400, — 
measures 245 mm. from the tip of the rostrum to the end of the telson. The 
rostrum of this specimen is 56 mm. long, the whole carapace, including 
rostrum, 116.5 mm. 
Hemipeneus triton Fax. 
Plate L., Fig. 1-1’. 
Bull. Mus. Comp. Zool., XXIV. 215, 1893. 
This species, like H. spinidorsalis, is remarkable for having a long, curved 
spine on the dorsal side of the third abdominal segment. It differs from 
HT. spinidorsalis in having a very much shorter rostrum and longer, more 
flattened, ribbon-like outer antennular flagella. The rostrum is shorter than 
in any previously described species, being much shorter than the eye-stalks ; 
it is armed above with two to four teeth, the posterior of which lies a little 
way behind the orbit; the fourth tooth, when present, is very minute, and is 
situate near the distal end of the rostrum. The rostrum is the same length 
