44 PROCEEDINGS OF THE NATIONAL. MUSEUM yol. 80 



the entire antenna on the dorsal surface of segments two to eight. 

 The entire genital segment is dilated to twice the width of the 

 abdomen; the latter has four segments, of which the basal and 

 terminal are twice the length of the other two. 



Color (preserved material). — Uniform yellowish white. 



Measurements. — Length: Female, 1 mm.; male, 0.85 mm. 



Occurrence. — Six specimens, including both sexes, were taken in a 

 bottom net at Station A on December 5, 1920, in water 46 metere 

 deep over a bottom of black mud. This station is well inside the 

 mouth of the bay, and the species may occur elsewhere. 



Types.— [5.^.'^. M. No. 58562, male, holotype; No. 63419, 1 male, 

 4 females, paratypes. 



Remarks. — This species is closely related to hrevifurcatus^ the type 

 of the genus, but differs in the greatly increased width and decreased 

 length of the cephalothorax of the female, and in the details of the 

 various appendages, especially the mouth tube and the first maxillae. 

 In Sars's figure of the female of hrevifurcatv^ the cephalothorax is 

 twice as long as wide and also twice as long as the remainder of the 

 body. In Giesbrecht's figure of the male the cephalothorax is only 

 one-fifth longer than wide, but is nearly twice as long as the re- 

 mainder of the body. These are very different proportions from 

 those here given. In the female Sars makes the mouth tube ten 

 times as long as its basal width, with the terminal portion exceedingly 

 slender and tapering regularly to the tip. Here the length is only five 

 times its basal width, and the terminal portion is stout and somewhat 

 enlarged at the tip. 



HEMICYCLOPS AMERICANUS, new species 

 Plate 5, A-H 



SpecifiG characters of female. — Body cyclopoid and fairly stout, 

 with the anterior division sharply separated from the posterior, 

 strongly depressed and obovate in outline. Cephalic segment consid- 

 erably wider than its length on the midline, and longer than the four 

 succeeding segments combined, with a small triangular rostral proc- 

 ess, invisible dorsally. Epimeral plates of the second, third, and 

 fourth segments close together and rounded at their posterior corners, 

 the fourth segment a little more than half the width of the cephalon. 

 Fifth segment abruptly contracted to half the width of the fourth, 

 swollen through the bases of the fifth legs, and strongly narrowed 

 anteriorly. Genital segment a little wider than fifth segment ante- 

 riorly but tapered posteriori}^, with a median transverse suture visible 

 at the sides but fading out on the dorsal surface. iVbdomen of three 

 segments slightly tapered, the basal segment the longest, the second 



