Rev. Canon A. M. Norman on British Mysidge. 147 



Fam. Mysidse. 



MaxiUipeds stoutly built ; cxopodite natatory, multiarticu- 

 late ; cpipodite lanceolate and projected into the branchial 

 cavity. First limbs of the trunk (here called the gnatho- 

 pods) are generally like in the general aspect of the endo- 

 podite to the maxillipeds ■^, and differ totally from the 

 following six pairs of legs^ which are all developed and have 

 their distal portion (iiere called tarsus) in most cases divided 

 into numerous setiferous articulations. Nail generally feeble 

 or absent, more rarely well developed. No true hranchice 

 present. Marsupial poucli composed of two or three (in 

 Boreomysis of seven) pairs of leaf-like processes springing 

 from the bases of the posterior legs. Pleopods in female 

 small and rudimentary, in male much more developed t ; 

 sometimes in tiiat sex all except the first are biramose and all 

 multiarticulate and natatory ; in other genera they are 

 variously modified and the third or fourth pair, or both these 

 pairs, are specially developed to subserve sexual functions. 

 Inner uropods with acoustic organ at their base. No phos- 

 phorescent organs. Telson very variable in form, but never 

 as in the Euphausiidse. 



Synopsis of Subfamilies. 



A. Outer uropods two-jointed, outer m.ni'gin of the 

 first joiut spiued. Telsou entire. Tarsus of legs 

 with only one or two joints, with a two-jointed 

 nail Cynthiliincc. 



J3. Outer uropods one-jointed, their outer margin 

 spined, Telson entire. Tarsus of legs multiarti- 

 culate Gastrosaccuxe. 



C. Outer uropods one-jointed, their outer margin 

 setose. 



1 . Gnathojyods conforming in general character of 



endopodite to the maxillipeds." 



2. Gnathopods conforming in general character to 



the first legs. 



1. — a. First legs greatly developed, very strong, and 

 much larger than the following, their tarsus 



* In Mysidella the gnathopods are quite different from the maxillipeds 

 and very like the first legs. 



t But in tile genera Ileteromysis and Mysidella the pleopods of the 

 two sexes are of similar character. 



