43 



with any dorsal crest; pseudorostral projection always distinct, triangular, and 

 horizontally extended; antero-lateral corners only slightly produced. Epimeral 

 plates of the pedigerous segments generally narrow and incrassated, those of 

 last segment sometimes produced to posteriorly-pointing spines. Caudal segments 

 constricted at the hase and also immediately in front of the posterior end, with 

 the lateral corners more or less projecting; last segment flattened, sub-pentagonal. 

 Eye generally present, and much larger in male than in female. Superior an- 

 tennae in female with the peduncle very slender, outer tiagellum 4-articulate, inner 

 3-articulate and much the smaller; those in male not very different, though 

 having the peduncle somewhat thicker, and the outer fiagellum 5-articulate with 

 the usual additional fascile of sensory filaments at the base. Inferior antennae 

 in female 4-articulate, with 4 plumose setae, one apical ; those in male, as a 

 rule, exceeding the body in length, last joint of the peduncle large and com- 

 pressed, being clothed below with comparatively short sensory appendages, fia- 

 gellum very slender, filiform, with rather elongate articulations. Mandibles large, 

 oblong, with the body regularly navicular in form. 3rd and 4th pairs of legs in 

 female with no rudiments of exopodites. Both pairs of pleopoda in male nor- 

 mally developed, with the rami well defined, the outer one biarticulate, the inner 

 uniarticulate. 3rd and 4th caudal segments in male with 4 plumose setae in place 

 of the pleopoda. Uropoda with the rami much shorter than the basal part, the 

 inner one mucroniform and, as a rule, shorter than the outer, which is very nar- 

 row, linear, and sparingly setiferous. Telson narrow lageniform, with the outer 

 part conically tapered and densely spinulous on each side; that in male geni- 

 culate in the middle, or exhibiting a projecting angle dorsally. 



Remarks. Of all the Cumacean genera this is the oldest as regards date, 

 having been established by the North American zoologist, Th. Say, as early as in 

 the year 1818. According to the general rule, the order should therefore more 

 properly have been named from this genus, and not from the genus Cuma, which 

 was established 10 years afterwards; but the term Cumacea is now so universally 

 accepted, that a change would be rather inconvenient. At any rate, the term 

 Dlastylidce proposed by Sp. Bate cannot, in consequence of its composition, be 

 used to designate the whole order, but must be restricted to one of the families 

 into which the order is divided. The present genus is the type of this family, and 

 even in the restriction here adopted, it is, of all the Cumacean genera, that which 

 comprises the greatest number of species, amounting at present to about 30 in 

 all. 10 of these species belong to the fauna of Norway, and will be described 

 below; among them are some of the largest known Cumacea. 



