TANAIS. 121 



joint armed with strong setae ; these two divisions are 

 fixed upon an oblong movable basal joint. The outer 

 pair of maxillae, according to Savigny, consists of a 

 pair of organs, each of which is formed of three slender 

 oval plates lying upon each other and arising from an 

 oblong basal joint. 



The pair of foot-jaws {g), closing the mouth from 

 beneath, is of large size, brought into contact with each 

 other along the inner edge of the basal half, the first 

 joint being nearly square, but with the base produced at 

 the inner angle ; the second joint is short, but swollen on 

 the outer edge and produced within into a flat oval plate, 

 ciliated along the margin ; the third and fourth joints 

 respectively are nearly triangular in form, with a strong 

 pencil of hairs on the inner margin ; and the terminal 

 joint is slender, curved, and affixed at the apex of the 

 preceding joint so as to rest upon its inner edge, the 

 top and inner margin being also furnished with a long 

 pencil of hairs. The organs of the mouth occupy nearly 

 the whole of the under-side of the conjoined head and 

 first segment of the body, leaving the laterally-dilated 

 posterior angles for the insertion, on the under-side, 

 of the base of the large first pair of legs. 



The first pair of legs are not only evidently very 

 powerful organs of prehension, but are also employed 

 by the animal for the defence of the parts of the mouth, 

 upon which, when unemployed, they fold very closely. 

 They are of large size and very robust, with the wrist 

 oblong, and the hand large and sub-ovate, set on the wrist 

 obliquely, having the infero-anterior angle produced into 

 a strong fixed finger, against which the movable apical 

 finger works, forming a powerful didactyle claw. The 

 second pair of legs are more slender than the remainder, 

 and somewhat longer than the third pair ; the segment of 



