ISOPODA OF THE ' LIGHTNING ' AND OTHEE EXPEDITIONS. 107 



sexes; hand elongated, fingers narrow and acuminate. 

 First peraeopods with very long setiform finger. Hinder 

 peraeopods with penultimate joint expanded, and furnished 

 with a knife-like spine, finger short. Uropods biranious, 

 branches 2-jointed. Marsupial pouch formed of only two 

 iobes Pseudotanais, G. 0. Sars. 



(b) Upper antennae with three articulations in female; in male 



much larger, with a 4-jointed flagellum. Gnathopods 

 nearly alike in both sexes, not very strong ; hand narrow, 

 fingers simple. First peraeopods with a setiform finger ; 

 the hinder pairs short, with their basal joints very tumid. 

 Uropods branched, each branch 1-2-jointed. Marsupial 

 pouch of usual character, composed of eight laminae . . Typldotanais, G. O. Sars. 



(c) Upper antennae in female 4-jointed, in male much larger ; fla- 



gellum 4-jointed, with large fascicles of sensitive cilia. 



Gnathopods in female moderately strong, hand dilated, 



fingers strong, the thumb serrulated ; in male more slender, 



with simple fingers. Peraeopods little differing from each 



other, more or less spinous. Pleopods sometimes not 



developed in female. Uropods 2-brancbed, inner 2- ( $ ), 



3- (cj) jointed; outer 1-2-jointed, or sometimes a mere 



tubercle Leptoynathia , G. O. Sars. 



Pleon segmented. Pleopods all developed and ciliated. Ocular 

 lobes and eyes present, 

 (a) Upper antennae in both sexes with a well-developed flagellum 



of about four joints, the flagellum in male with fascicles of 



sensitive cilia. Gnathopods of usual form in female ; finger 



and thumb strong, the latter with tuberculated palm ; in 



male largely developed, oblong, finger and thumb curved, 



forcipiform, both strongly toothed within. Peraeopods 



much spined, the spines very variable in structure. Uro- 

 pods 2-branched, inner multiarticulate (8-9-jointed) ; outer 



2-jointed. No eyes Alaotanais, n g. 



(p) Upper antennae 3-jointed in female, 6-jointed in male, and 



furnished with bundles of sensitive cilia. Gnathopods not 



very dissimilar in the sexes ; hand oblong, fingers short. 



Peraeopods of first pair slightly differing from the rest, with 



a long setiform finger ; hinder pairs with first joint 



rather swollen. Uropods with two subequal 2-jointed 



branches Paratanais, Dana. 



(c) Upper antennae with three joints and rudimentary flagellum 



in female ; narrow and elongated, with a more or less 



developed flagellum in male. Gnathopods in female of the 



usual structure ; but in the male imperfectly chelate, 



without any finger, or the finger very short and immovable. 



