REPOET ON THE OSTRACODA. 141 



of deep water, these localities ranging from 1375 to 2050 fathoms, while, as to geographical 

 distribution, the range is over the Pacific Ocean, from Japan to Patagonia ; and probably 

 also over the Atlantic, seeing that the neighbourhood of the Azores also yielded specimens. 

 [PL XXXIII. fig. 8, a~d. a Shell seen from left side, h from above, c from below, 

 d from front. All magnified 50 diameters.] 



Bythocythere, G. 0. Sars (1865). 



Valves subequal, smooth, or sparingly sculptured, almost destitute of hairs ; thin 

 and fragile ; hinge-joint quite simple, or composed of a slight bar and furrow ; no 

 teeth. Anterior antennae elongated, seven-jointed ; the second joint large and thick, 

 and bearing a seta on its anterior and posterior margins ; the other joints suddenly 

 much narrower, forming a long slender lash, which bears several setae ; penultimate 

 joint linear, and destitute of setae. Posterior antennae tolerably robust, four-jointed ; 

 second joint large ; flagellum long, biarticulate, its last joint long and setiform. Man- 

 dibles constricted above the distal extremity, and strongly toothed ; palp four-jointed, 

 bearing a well- developed branchial plate, which is set with numerous ciliated setae. 

 Terminal lobes of the first pair of jaws very short and thick ; branchial plate large, 

 ovate, bearing numerous marginal cUiated setae, and at the base four long, deflexed simple 

 setae. Feet elongated, terminal claw very long and slender, second and third joints 

 bearing each a short apical setae ; basal joint of the first pair furnished at the base 

 with a small lobe which bears two very large and densely ciliated, and two smaller and 

 simple setae. Abdomen ending in a very large and acuminated process ; postabdominal 

 lobes narrow and bearing three hairs. Eyes mostly absent. 



This genus is very nearly allied to Cytlieropteron, and, like it, is represented in the 

 Northern Seas, and in the British Post-Tertiary deposits, by two tolerably abundant 

 species, — Byiliocy there simplex (Norman), and Bythocythere constricta, G. 0. Sars, — as 

 well as by others which are less common. 



1. Bythocythere orientalis, G. S. Brady (PL VI. fig. 6, a-d, and PL XXXII. fig. 2, a-c). 



Bythocythere orientalis, Brady, Les Fonds de la Mer, torn. i. p. 159, pi. x\d. figs. 21-23. 



The outline of the shell of this species is very closely similar to that next to be 

 described {^Bythocythere arenacea), difi'ering from it chiefly in having the lateral view 

 less acutely pointed behind, the surfaces, both ventral and lateral, less convex, and the 

 shell quite devoid of tubercular ornamentation. The ventral surface is marked with 

 irregular, sinuous, longitudinal furrows, and the general surface is vaguely undulated. 

 Length, l-48th of an inch ('52 mm.). 



One or two detached valves only found in anchor mud, from a depth of 7 fathoms in 

 Hong Kong Harbour, from which place the type-specimens also were brought. Specimens, 



