646 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 41. 



of minute square-cut teeth. The pseudorostrum is short, horizontal, 

 and deeply grooved on the dorsal surface. There is no ocular lobe. 

 The anterior part of the lower edge of the carapace is serrated, with 

 square-cut teeth. 



The surface of the free thoracic end of the abdominal somites is 

 finely roughened. The pleural plates of the second free somite are 

 rounded anteriorly and hardly overlap the somite in front. 



The abdomen, excluding the telson, is about as long as the cepha- 

 lothoracic region. 



The telson is about as long as the last somite and reaches to about 

 the middle of the uropod peduncles ; the basal part is slightly expanded ; 

 the post-anal part is about equal in length to the pre-anal; there are 

 generally two pairs of lateral spines (sometimes two spines on one side 

 and one or three on the other) and a pair of larger apical 

 spines. 



The peduncle of the antennule has the last segment 

 longer than either the 

 first or second. Pen- 

 ultimate segment of 

 antenna not elon- 

 gated. 



Third maxilliped 

 with basis not ex- 

 panded or produced 

 distally. Ischium and 

 merus of about equal 

 width, the latter with 

 (?) two teeth exter- 

 nally. 



First legs with basis 

 bent nearly to a right angle about the middle of its length; its length 

 along the inner edge a little less than that of the distal segments 

 together. Basis of second legs somewhat expanded internally, cai-pus 

 about as long as the last two segments together. Posterior legs rather 

 short and stout, third and fourth pairs without exopods. 



The peduncle of the uropods has about ten spines on its inner edge. 

 The exopod is less than half as long as the peduncle and longer than 

 the endopod; the tlu-ee segments of the latter are well defined, the 

 proximal twice as long as either the second or third. Proximal seg- 

 ment of the exopod nearly one-half as long as the distal. i 



Remarks. — This pretty species is unlike any other known to me in 

 the shape and ornamentation of its carapace, and it is not easy to 

 suggest in what direction its immediate allies are to be sought. : 



Locality. — Cape Smyth, Alaska; 2 J fathoms; Point Barrow Exped., 

 August, 1883; U.S.N.M. 7937, 44053; 10 females, mcluding holotype 

 (7937). 



63 64 



Figs. G3-65.— Diastylis nucella, female. 63, Anterior part op 



BODY FROM ABOVE; 64, FIRST LEG; 65, LAST SOMITE, TELSON, AND 

 UROPOD. 



