395 



Page 211. 

 Add the following species: 



Mesochra exigua, G. 0. Sars, n. sp. 



(Suppl. PI. 26, fig. 1). 



Specific Characters. Female. Body comparatively short and stout, slightly 

 depressed in front, with the anterior division somewhat broader than the posterior. 

 Rostral prominence well marked, subtriangular in form, with the tip obtusely 

 rounded. Urosome nearly as long as the anterior division and only very slightly 

 tapered hehind, last segment well developed, though a little shorter than the 

 preceding one. Caudal rami very small and placed rather far apart; apical setee 

 normal and of moderate length. Anterior antennae comparatively short and only 

 composed of 5 joints densely clothed with rather strong setae, the 3 first joints 

 belonging to the proximal part, the last 2 to the terminal part, the latter 

 occupying not fully half the length of the antenna and having the 1st joint short, 

 the 2nd elongate fusiform. Posterior antennae with the outer ramus small, but 

 distincly biarticulate. Mandibular palp with a slight rudiment of an outer ramus. 

 Posterior maxillipeds of moderate size and normal structure. 1st pair of legs 

 with both rami distinctly 3-articulate, the outer one a little shorter than the 

 inner, with no seta inside the middle joint, its last joint the largest and armed 

 with 3 spines and 2 curved setse; inner ramus imperfectly prehensile, 1st joint 

 somewhat dilated and, like the 2 succeeding joints, provided inside with a ciliated 

 seta, last joint longer than the midle one and armed on the tip with a claw-like 

 spine and a slender curved seta; both these joints combined considerably 

 exceeding the length of the 1st. Natatory legs with the outer ramus long and 

 slender, inner much shorter and only composed of 2 joints. Last pair of legs 

 with the distal joint oblong conical in form and edged with 5 rather unequal 

 setse; inner expansion of proximal joint triangular and extending about to the 

 middle of the distal joint, marginal setse 5 in number, the outermost but one 

 the longest. 



Colour not yet ascertained. 



Length of adult female 0.45 mm. 



Remarks. This form in some respects differs rather conspicuously from 

 the other known species comprised within the genus Mesochra of Boeck. As 

 however the structure of the natatory legs is that caracteristic of the said genus, 

 I find it appropriate to describe it as a member of that generic group. 



