RECENT BRITISH OSTRACODA. 



391 



highest in the middle, and sloping steeply behind; ventral gently sinuated in front, and 

 slightly convex behind. Seen from above, the outline is compressed, oval ; extremities 

 equally and rather obtusely pointed ; greatest width in the middle, equal to about one- 

 third of the length. Hinge-line slightly sinuous. The left valve overlaps considerably 

 on the dorsum and in the middle of the ventral surface. Shell smooth, colour pale 

 ochreous or white, opaque. Animal unknown. 



Length in., height ^q- in. - ' - . . 

 Hah. The Minch, 45-60 fathoms [Mr. Jeffreys). 



This very fine and distinct species occurred in the same dredgings with Ti. obtusata, 

 and though more abundant than the latter species, must still be considered rare. 



Genus 8. Macrocypris, Brady*. 



Carapace much elongated, attenuated at the extremities. Valves unequal, the right 

 larger than the left, and overlapping dorsally; hinge-line flexuous. Surface smooth, 

 polished, and destitute of hairs. Antennae short and robust, the superior seven-jointed, 

 joints tapering towards the apex, bearing short setse ; the inferior composed of five 

 distinct joints, last two joints very short ; armed with much-elongated claws ; second 

 joint bearing on its inner side near the base a bundle of short biarticulate setae. Man- 

 dibles large, dilated at the inferior extremity, and divided into six or seven strong 

 teeth ; palp elongated, four-jointed, and having a distinct branchial appendage. Pirst 

 pair of jaws provided with an unusually small subovate branchial plate ; external lobe 

 or palp narrow, not larger than the rest. Second pair of jaws destitute of a branchial 

 appendage; palp, in the female, large and subpediform, composed of four distinct joints, 

 the last armed with three claws or spines ; in the male very robust and subclieliform. 

 Eirst pair of feet much elongated, five-jointed, last joint armed with one or two long 

 forward-curved claws ; the second pair very different, and covered entirely by the shell, 

 five-jointed, last joint armed with a very long recurved claw. Postabdominal rami 

 rudimentary, forming two small and simple appendages attached to the posterior part of 

 the abdomen. No eye. Male smaller than the female ; copulative organs large and 

 provided at the anterior extremity with a much-elongated mucus-gland. 



The species constituting this genus are included by Sars under Bah^dia ; that author, 

 however, had had no opportunity of examining the animals belonging to the grouj) 

 typified by B. suhdeltoidea, to which the name Bairdia was originally given by M'Coy. 

 I have myself so far succeeded in the investigation of the animal structure as to find 

 ample generic characters in the formation of the postabdomen, though the other portions 

 of its anatomy remain to be worked out. But, in addition to peculiarities of animal 

 structure, the carapace presents well-marked differences, in its attenuated form and in 

 the respective size of the valves, the right being here much the larger. 



Sars observes that this marine genus seems to be analogous to the freshwater genus 

 Candona, just as Bontocypris appears to be the marine equivalent of Cyxjris. The 

 only British species is 



* Intellectural Observer, vol. xii. p. 119. 



