RECENT BRITISH OSTRACODA. 



465 



I have not succeeded in detecting the sexual organs of the two species belonging to 

 this genus ; but it seems pretty certain that the forms referred to in the generic de- 

 scription are really the two sexes of one and the same species. The shells of the two 

 forms present no appreciable difference ; and the several pairs of jaws, the mandibular 

 and " oviferous " feet, and the postabdominal laminae are in both precisely alike. 



1. Cylindrolebeiiis Mahijs (Baird). (Plate XXXIII. figs. 18-22, and Plate XLI. 



fig. 1.) 



Cypridina Maria:, Baird, Proceedings Zool. Soc. Lond. part xviii. (1850) p. 257, pi. xvii. (Animlosa) 

 figs. 5-7. 



Carapace, as seen from the side, oblong-elliptical, more than twice as long as high, 

 rather higher in front than behind. Dorsal and ventral margins nearly straight, sub- 

 parallel ; beak erect ; notch wide, almost rectangular. Extremities obtusely rounded, 

 the posterior rather narrowed. Outline, as seen from above, oblong, subclavate, about 

 twice as long as broad, greatest width in front of the middle ; extremities rounded, the 

 anterior deeply cleft in the centre. Notch radiated, produced along the median lines of 

 the dorsal and ventral aspects as well as laterally. End view nearly circular. Muscle- 

 spots very numerous, forming a conspicuous patch near the centre of the valves. Shell 

 pellucid, and showing through it the deep-yellowish-brown body of the animal ; growing 

 altogether opaque with age. Eyes black and plainly visible through the shell, rather 

 behind and above the centre. Upper antenna? of the male altogether more slender and 

 less densely setose than in the female ; auditory seta short and stout, dilated and 

 obliquely truncate at the apex ; terminal claw also short and stout, scarcely half the 

 length of the adjacent setae. Second joint of the natatory branch of the lower antennae 

 in the female short, scarcely longer than the following joints ; in the male nearly as long 

 as the first joint. Eirst pair of maxillae subquadrate, bearing a large branchial appen- 

 dage. Oviferous foot terminating in two equal numerously dentate lips ; setae robust, 

 rather irregularly spined toward the apices. Postabdominal laminae broad, subquadran- 

 gular, obliquely truncate behind, armed with six slender marginally dentate, slightly 

 curved claws, which decrease regularly in length from below upwards. 



Length in. : 



Hah. Isle of Skye [Dr. Baird) ; Shetland, Penzance, and with the preceding species in tide-pools at 

 Herm [Rev. A. M. Norman) ; taken in the towing-net at Cumbrae [Mr.D. Robertson). 



C. MaricB, though mostly taken in company with Fhilomedes longicornis, is a much 

 scarcer species, the specimens taken at any one time being never very many. 



2. Cylindroleberis teres (Norman). (Plate XXXIII. figs. 6-9, and Plate XLI. fig. 2.) 



Cypridina teres, Norman, Ann. & Mag. Nat. Hist. vol. viii. (Oct. 1861) pi. xiv. fig. 10. 



Carapace of the female, as seen from the side, ovate, highest behind the middle ; 

 greatest height equal to more than two-thirds of the length; extremities rounded, 

 anterior narrowed, posterior broad ; superior and inferior margins evenly convex ; notch 

 very narrow, curved. Outline, as seen from above, ovate, widest in the middle, more 



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