REPORT ON THE OSTRACODA. 41 



last two joints very short ; terminal claws elongated; second joint bearing a bundle of short 

 Inarticulate setaj. Mandibles large, dilated, and armed with six or seven strong teeth ; 

 palp elongated, four-jointed, and provided with a branchial appendage. The first pair 

 of jaws have an unusually small, subovate branchial plate, and the external segment is 

 narrow, and not larger than the rest ; second pair destitute of a branchial appendage ; 

 palp in the female, large and subpediform, four-jointed, the last joint armed with three 

 claws ; in the male, very robust and subcheliform. First pair of feet much elongated, 

 five-jointed, last joint armed with one or two long curved claws ; second pair very 

 different, covered entirely by the shell, five-jointed, terminal claw very long and recurved. 

 Postabdominal rami rudimentary, forming two small simple ajjpendages attached to 

 the posterior part of the abdomen. No eye. Male smaller than the female ; copulative 

 organs large ; spermatic glands long and narrow, the lateral filaments apparently not 

 arranged in a verticellate manner. 



The type of this genus, Macrocypris minna, was included by G. 0. Sars under 

 Bairdia, he having had no opportunity of investigating the anatomy of the animal. 

 The shell, however, differs distinctly from that of Bairdia in having the right valve 

 instead of the left the larger ; while as to the structure of the contained animal, the 

 presence in Macrocypris of two pairs of jaws, the flexuous second foot, and the rudi- 

 mentary postabdominal rami, besides other differences, are amply sufficient to separate 

 the one genus from the other. 



1. Macrocypris tenuicauda, n. sp. (PI. II. fig. 1, a-f, and PI. III. fig. 2, a, h). 



Carapace elongated, siliquose ; seen from the side subtriangular, highest in the middle, 

 narrowly rounded in front, much attenuated, and subacuminate behind ; dorsal margin 

 strongly arched, and sloping steeply from the middle to each extremity, ventral slightly 

 sinuated in front ; height equal to rather more than one-third of the length ; seen from 

 above the outline is broadly ovate, widest near the middle, and tajjering evenly to the 

 extremities, which are acuminate ; width and height nearly ec^ual ; the end view is sub- 

 circular, but somewhat angulated above, and keeled below ; the left valve (PI. II. fig. 1, e) 

 is much narrower than the right (fig. 1,/), and has its dorsal arch truncated. Shell 

 perfectly smooth, dense in structure, whitish. Length, l-16th of an inch (r55 mm.). 



This species seems to be not very widely distributed ; the only dredgings in which I 

 have met with it being those from off Culebra Island, West Indies, 390 fathoms, mud 

 (Station 24) ; and off North Brazil, 350 fathoms, mud (Station 122). In both of these 

 it occurred abundantly, though the specimens were for the most part separated valves. 

 From some of the more perfect specimens I have been able to satisfy myself as to the 

 structure of the contained animal, and this, together with the characters of the shell, is 

 sufiicient to identify the genus to which it belongs. 



[PI. 11. fig. 1, a-f. a Carapace seen from left side, h from above, c from below, d from 



(ZOOL. CHALL. ESP. — PART III. 1880.) C 6 



