42 



joints narrow and elongated, forming angular bends with each other; 2nd pair 

 likewise slender, though shorter, and exhibiting the full number of joints. Both 

 these pairs in female with well-developed natatory exopodites, the 3 posterior pairs 

 simple. All the legs in male, except the last pair, provided with very fully de- 

 veloped exopodites. Pleopoda in male only 2 pairs. Uropoda slender, with the 

 basal part very narrow and spinulose inside, inner ramus triarticulate, outer bi- 

 articulate. Telson well defined, with the outer part generally narrowly produced 

 and spinulous, tip with only two spinules. Sexual dimorphism generally very 

 pronounced. 



Remarks. This family is well distinguished from the other Cumacean 

 families by a number of easily recognizable characters. As to the external ap- 

 pearance, the sharp demarcation between the anterior and posterior divisions of 

 the body is rather characteristic, the former being generally very tumid, whereas 

 the latter is always extremely narrow, with the segments connected in a parti- 

 cular manner, so as to admit of very great mobility, not only in a ventral, but 

 also in a dorsal direction. In all the known forms, the anterior extremity of the 

 body is produced in a nose-shaped prominence, the pseudorostral projection, and 

 the posterior in a more or less elongated, narrowly lageniform piece, the telson, 

 which projects between the slender, diverging uropoda. The structure of the an- 

 tennas is rather unlike that in other Cumacea, and in the structure of the other 

 appendages also, several peculiarities are to be found. As to the number of 

 pleopoda in the male, this family agiees with the Leuconidce, but is otherwise 

 very different. The family comprises as yet 5 genera, 4 of which are represented 

 in the Norwegian fauna and will be treated of below, the 5th. Pachystylis, having 

 recently been established by Dr. Hansen, to include an exotic form from the 

 German Plankton-Expedition. 



Gen. 1. DiastyllS, Say, 1818. 



Syn: Condylura, Latreille (not Illiger). 

 Alauna, Goodsir. 

 Cuma, Kreyer (not Edwards). 



Generic Characters. Body in female rather robust, in male much more 

 slender. Integuments generally hard and brittle, exhibiting an irregular reticulated 

 structure, and more or less densely hairy. Carapace large and tumid, not infre- 

 quently armed with spiniform projections, sometimes also with lateral folds, but never 



