310 



HISTOKY OF RECENT CRUSTACEA 



Famihj 8. —Diastylida'. 



The first antennae ave more or less unlike in the two 

 sexes, the flagella unequal, the smaller being three-jointed 

 in the female. The anterior branch of the mandibles has 



i'lG. 27. — DiastylU GoodsiH, lateral 

 view of female CHanseu], 



Fig. 26. — Diastylis Goodsiri, dorsal view 

 of female [HanseD]. 



a dense series of lateral spines. The epipod of the first 

 maxillipeds has tlie branchial sacs arranged more or less 

 spirally. The third maxillipeds have the second joint very 

 large and curved. The first two pairs of perseopods in the 

 female and the first four in the male have well-developed 

 swimming-branches. There are only two pairs of pleopods 

 in the male, and of these the second is sometimes imper- 

 fectly developed. The uropods have the inner branch 

 two- or three-jointed. The telson is distinct, generally 

 narrowed terminally, with only two spines at the apex. 



The family includes three genera. 



Biastylis, Say, 1818, is the earliest in date of the 

 Cumacean genera, and in Lepechin's Oniseus scmyioides, 



