62 AMPniPODA NOUMALIA. 



of the second pair of pereiopoda very deeply excavated upon the 

 upper part of the posterior margin to receive the coxa of the 

 third pair of pereiopoda. The two pairs of gnathopoda subcqual 

 and uniform. Mandibles having an articulated appendage. Max- 

 illipeds pediform, ha^■ing a rudimentary squamiform plate on 

 both the basos and ischium joints. The three posterior pairs of 

 pleopoda alike, stylifonn, double-branched. Telson simple, squa- 

 miform. 



This genus differs from Stenothoe in having an appendage to the 

 mandibles and two rami to the posterior pair of pleopoda. The 

 species of this genus are generally more or less tuberculated. 



1. Pleustes tuberculatus. (Plate IX. tig. 8.) 



Pleustes tubercidata, Spence Bate, Ann. %■ Mac/. Nat. Hist. ser. 3. vol. i. 

 p. 362, 1858. 



Cephalon produced into a sharp rostrum. Dorsal surface of the 

 pereion and the anterior part of the pleon carinated ; an elevation 

 on each side of the carina on the anterior segments of the pereion, 

 which gradually increases posteriorly until it as,sumes the fonn 

 of a tubercle, highest upon the second segment of the pleon, 

 and widest (plate -like longitudinally) upon the third and fourth, 

 and continued smaller to the last : lateral to these, a second 

 row of tubercles, or rather obtuse ridges, commencing with the 

 first, and traversing the margin of all the segments of the 

 pereion and the first two segments of the pleon, in a continuous 

 Urie. Analogous eminences exist upon the coxae of the three 

 posterior paii's of pereiopoda. Eyes round. Superior antennae 

 longer than the inferior. Gnathopoda subequal, ovate; palm 

 extremely oblique, nearly as long as the inferior margin, furnished 

 with two small teeth at the inferior angle. Thi-ee posterior pairs 

 of pereiopoda subequal. Posterior paii' of pleopoda like the two 

 preceding, but shorter, styliform, naked, double -branched, the rami 

 unequal. Telson quadrate, squamiform. 

 Length yjths of an inch. 



Hah. Arctic Regions. 



The type, on which the genus is founded, and from which this 

 species is figured, is in the Museum of the CoUege of Siu-gcons, to the 

 Council of which I am indebted for the loan of this and many other 

 specimens. The habitat of the animal Ls not specified ; but I foim^d 

 it in a bottle along with other known Ai'ctic species. I am also in- 

 debted for the loan of a specimen to Mr. Albany Hancock, which 

 was di-edged in N. lat. 66° 30', W. long. 68°, by Messrs. Warham 

 and Harrison. 



