241 



Remarks. This new genus is proposed, to include the large Cytherid 

 originally recorded by Norman under the name of Cythere simplex and sub- 

 sequently described by the present author as a new species of his genus 

 By ihocy there. True, this form agrees in most of the structural details rather 

 closely with that genus; but the shell is of a very dissimilar appearance, and 

 I have also found some well-marked differences in the structure of the appen- 

 dages, making it convenient to discard it as the type of a particular genus. 

 Among these differences it is whorthy to name the very conspicuous transfor- 

 mation of the last pair of legs in the male, not found in any other Cytherid 

 known to me. 



133. Macrocythere simplex, (Norman). 



(PI. CX). 



Cythere simplex, Norman, Nat. Hist. Trans. Northumb. & Durham, Vol. 1, p. 17, PI. V. figs. 14. 

 Syn: Bythocythere acuminata, G. O. Sars. 



Specific Characters. Female. Shell, seen laterally, elongate oval in shape, 

 a little higher behind than in front, greatest height not nearly attaining half 

 the length, dorsal margin only very slightly arched and joining the anterior 

 and posterior edges without any intervening angle, ventral margin distinctly 

 sinuated in front of the middle and gently bowed behind, anterior extremity 

 evenly rounded off, posterior gradually contracted to a sharp point located 

 about in the longitudinal axis of the shell; seen dorsally, narrow oblong in 

 outline, with the greatest width about in the middle and scarcely exceeding 

 Va of the length, side-edges evenly curved, anterior extremity obtusely pointed, 

 posterior gradually tapered to a narrow conical prominence. Valves of rather 

 fine consistency, but very pellucid, with the surface perfectly smooth and polished, 

 not exhibiting any obvious sculpture, inner duplicature well defined and rather 

 broad, marginal zone highly chitinised ^and crossed by numerous fine pore- 

 channels, edges smooth and almost bare of hairs. Anterior antennae with the 

 terminal part scarcely longer than the basal one, and clothed with scattered 

 thin setae. Posterior antennae with the 1st joint of the terminal part nearly 

 twice as long as broad, middle joint of equal width throughout and provided 

 anteriorly near the end with a well-marked setiferous ledge, apical claws rather 

 slender and successively increasing in length posteriorly. Legs slender, and 

 scarcely differing in structure from those in Bythocythere. 



Male of about same size as female, but differing somewhat in the shape 

 of the shell, which is conspicuously more expanded behind, with the dorsal 

 margin straight or even a little concave in the middle. Last pair of legs very 



30 Crustacea. 



