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PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 41. 



half than the last two segments together. The legs of the third and 

 fourth pairs have each a minute exopod of two segments. 



The peduncle of the uropods is spinous on the inner edge. The 

 exopod is a little less than half as long as the peduncle and very 

 slightly longer than the endopod; the three segments of the latter 

 are well defined, the first equal to or shorter than the other two 

 together; the inner edge of the endopod is spined, and the short, stout 

 apical spine is well defined at the base. 



Adult male. — Total length, 10.6 mm. 



Sculpture of carapace resembling that of female, but with only five 

 conspicuous transverse ridges, that corresponding to the hindmost 

 ridge of the female being barely traceable; in addition, a horizontal 

 ridge on each side runs forward from the hind margin 

 to the last transverse ridge a little way above the lower 

 edge of the carapace. The pleural plates of the third 

 free thoracic somite overlap those of the somite in front ; 

 the lateral processes of the last thoracic somite are short 



53 54 55 56 



Figs. 53-56.— Diastylis alaskensis, female. 53, Third maxilliped; 54, first leg; 55, third leg; 

 56, last somite, telson, and uropod. 



and blunt. The first two abdominal somites have each a small median 

 ventral spine. The telson is about one and a half times as long as 

 the last somite; the dorsal protuberance is at about the middle of its 

 length. The antennal flagellum is about as long as the body. 



Remarks. — This species is evidently allied to the two preceding, but 

 it differs from them in the greater number of ridges on the carapace, 

 which give it an annulated appearance. With the possible exception 

 of D. hidentata it would seem to be the most abundant Cumacean in 

 Alaskan waters. 



Localities.— hait.6S° 37 '00'' N.; long. 165° 19' 00" W.; 12 fathoms; 

 G. M. Stoney, June, 1884; U.S.N.M. 44019; 1 male. 



Albatross station 3600; Bering Sea; lat. 55° 06' 00" N.; long. 163° 

 28' 00" W. ; 9 fathoms; bottom temperature, 40° F.; U.S.N.M. 44020, 

 44021; many, male and female (including holotype, 44020). 



