NO. 1S76. ON THE CRUSTACEAN ORDER CUMACEA—CALMAN. 



641 



DIASTYLIS ALASKENSIS, new species. 



Ovigerous female. — Total length, 13.5 mm. 



Carapace less inflated than in D. scorpioides, its greatest height 

 about half of its length, narromng forwards from the hind margin as 

 seen from above; with six transverse ridges more or less completely 

 encircling it and with the hind margin strongly everted. Pseudo- 



FlG. 51.— DiASTYLIS ALASKENSIS, FEMALE, FROM THE SIDE. 



rostrum rather long and acute, the lateral plates meeting for a dis- 

 tance equal to twice the length of the ocular lobe. The ocular lobe 

 is a little longer than broad and its anterior end forms the dorsal part 

 of the first transverse ridge. 



The pleural plates of the second free thoracic somite are rounded 

 anteriorly and hardly overlap the somite in front. The dorsal part 

 of the fourth somite is not conspicuously produced 

 backwards. The abdomen (excluding the telson) is 

 a little shorter than the cephalothoracic region. 



The telson is very slightly longer than the last 

 somite and reaches to about the distal third of the 

 uropod peduncles. It narrows slightly from the base 

 to a rather sudden constriction about the middle of 

 its length; the post-anal division is about three- 

 fourths as long as the pre-anal. There are about six 

 pairs of lateral spines and a pair of somewhat larger 

 apical spines closely approximated. 



Peduncle of antennule with last segment slender, 

 longer than second, first much shorter than the other 

 two together. Penultimate segment of antenna elon- 

 gated. 



Third maxilliped with basis expanded distally; its 

 length along the inner edge about four and one-half times its greatest 

 %vidth, merus not expanded externally, narrower than ischium. 



First pair of legs with basis about as long as the distal segments 

 together, without conspicuous teeth; propodus longer than either 

 carpus or dactylus. In the second pair the carpus is longer by one- 

 94428°— Proc.N.M.vol.41— 11 41 



Fig. 52.— DiASTVLis 



ALASKENSIS, FE- 

 MALE, ANTERIOR 

 PART OF BODY FROM 

 ABOVE. 



