484 BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



than trunk, decreasing in diameter backward ; trunk cylindrical, the 

 portion representing the genital segment one-fourth as long as the 

 neck, four times as long as wide ; the portion representing the abdo- 

 men filiform, half as long as the neck, thirty times as long as wide. 

 First two pairs of legs biramose, third and fourth pairs uniramose, 

 all the rami 2-segmented and armed with plumose setae. Total 

 length, 40-50 mm. Egg strings, 10-15 mm. long. 



Remarhs. — ^The head of this parasite is buried close to the back- 

 bone of its host and is surrounded by a fibrous membrane or sheath 

 so tough that it is seldom removed without injury to the parasite's 

 head. Unlike the preceding species, there is rarely more than a 

 single specimen on each host, usually at one side of the dorsal or 

 ventral fin near the tail. 



Genus SARCOTRETES Jungersen, 1911 



Female. — Head fused with the first segment and in line with the 

 body axis, armed with two large and soft lateral horns turned 

 backward and tipped with a single dactylose process. Neck con- 

 stricted behind the horns, then enlarged, then narrowed a second 

 time where it joins the trunk, and usually more or less flexed. Trunk 

 claviform and squarely truncated posteriorly, the abdomen a mere 

 knob on the dorsal surface at the posterior end; no caudal rami. 

 First antenna with few segments ; second antenna chelate ; two pairs 

 of maxillae; no maxillipeds; first two pairs of legs biramose, third 

 pair uniramose, rami all 2-segmented and armed with plumose setae ; 

 fourth and fifth legs lacking. 



Copepodid male. — Head fused with first segment, three times as 

 long as wide ; second, third and fourth segments free ; fifth and geni- 

 tal segments and abdomen fused into a trunk without lobes; caudal 

 rami short and wide, each with four or five nonplumose setae. First 

 two pairs of legs like those of the female, biramose, rami 2-seg- 

 mented; third legs uniramose, rami 1-segmented; fourth and fifth 

 legs lacking. One species. 



SARCOTRETES LOBATUS Wilson 



FiGxmE 291 

 Sarcotretes lobatus Wh-son, Proc. U. S. Nat. Mus., vol. 53, p. 72, pi. 8, 1917. 



Occurrence. — Found buried in the flesh of the deep-sea lantern 

 fish {Benthosema nvillleri), captured off Marthas Vineyard and off 

 Block Island, 1885. 



Distribution. — Not found outside the present area. 



Color (preserved material). — Body a brownish yellow, darker on 

 the cephalothorax and trunk, lighter on the neck. 



Female. — Head cylindrical and strongly inflated; horns also in- 

 flated and cushionlike; neck behind the horns showing the two 



