Vv FAMILIES OF CUMACEA 120 
epipodite and a large gill upon the basal joints. Pleopods are 
only developed in the male sex. 
The flagellum of the second antennae in the male may be 
enormously elongated, as in the Atlantic deep-sea species shown 
in Fig. 80, so as to exceed in length the rest of the body. 
Fam. 1. Cumidae.—No sharp demarcation between thorax 
and abdomen. Four posterior pairs of legs in both sexes with- 
out exopodites. Male with five well-developed pleopods in addi- 
tion to the uropods. Telson wanting. Cuma, Cyclaspis, ete. 
Fam. 2. Lampropidae.— Body -form resembles that of 
Cumidae. All the thoracic limbs except the last have exopodites. 
The male has three pairs of pleopods. Telson present. Lamprops, 
Platyaspis, ete. 
Fam. 3. Leuconidae—Pody-form similar to above. Male 
has only two pairs of pleopods. Mouth-parts peculiar, much less 
setose than in other families. Telson absent.  eucon, Eudorella. 
Fam. 4. Diastylidae.— Anterior part of thorax sharply 
marked off from posterior part. Male has two pairs of pleopods. 
Telson present. Diastylis (Fig. 80). D. goodsivi from the Arctic 
ocean measures over an inch in length. 
Fam. 5. Pseudocumidae—Rather similar to Diastylidae, 
but differ in reduced size of telson and presence of exopodites 
on third and fourth thoracic legs of female. This family is 
represented by three very similar marine forms of the genus 
Pseudocuma; but, as Sars has shown,’ the Caspian Sea contains 
thirteen peculiar species, only one of which can be referred to the 
genus Pseudocuma, while the rest may be partitioned among four 
genera, Pterocuma, Stenocuma, Caspiocuma, Schizorhynchus. 
Order III. Isopoda. 
The Isopoda and the Amphipoda are frequently classed together 
as Arthrostraca or Edriophthalmata, owing to a number of features 
which they share in common, as, for instance, the sessile eyes 
which distinguish them from the podophthalmatous Schizopoda 
and Decapoda, the absence of a carapace, and the thoracic limbs 
which are uniramous throughout their whole existence. For the 
rest, in the presence of brood-plates and the other diagnostic 
1 Sars, ‘‘Crustacea Caspia,”’ Bull. Acad. Imp. Sci. St. Pétersbowrg, series 4, 
xxxvi., 1894, and ‘‘ Crustacea of Norway,” iii., 1900, p. 120. 
