RECENT BRITISH OSTRACODA. 



473 



first two joints larger than tlie rest, and forming between them a distinct genic'jlation ; 

 lower antennte composed of a large, broad, biarticulate, and geniculate basal portion, from 

 which arise two flattened unequal branches, one biarticulate, the other triarticulate, both 

 beset with very numerous long setee. Labrum large, subglobose, giving out in front a 

 short subtriangular process. Mandibles very weak, strongly inflexed at the lower 

 extremity, which is obliquely truncate and set in a pectinate manner with slender teeth ; 

 palp large and elongate, almost straight, bearing on the inner side very numerous long 

 pectinately arranged setae, which stretch backwards as in the feet of the Sididae. Pirst 

 pair of jaws bearing at the base a very large branchial plate, which is beset with numerous 

 ciliated marginal setae ; incisive portion divided into three setiferous lobes ; palp very 

 large, scarcely articulated; the posterior margin slightly lobated; the inner margin 

 pectinately setose, like the mandibular palp, but smaller. Second pair of jaws membra- 

 naceous, bearing, like the preceding pair, a branchial plate, but smaller and narrower ; 

 distal portion subovate, beset with a few ciliated setae, and in the male furnished with a 

 very large and strong hatchet-shaped apjiendage adapted for prehension. Third pair of 

 jaws, in the female, rudimentary, forming a simple setiferous lobe ; in the male strong, 

 distinctly jointed and subcheliform. Abdomen beset behind with several bundles of long 

 setse for supporting the ova. Postabdominal laminse narrow, slightly dilated at the apex, 

 and armed before and behind with several marginal setse or spines. Copulative organs 

 of the male very large and narrow." 



Prom this definition of the genus it will be seen that it difi'ers very remarkably from 

 all hitherto known forms, presenting, in the conformation of the lower antennse, a remark- 

 able approach to the Copepoda, and in the palps of the mandibles and first pair of jaws 

 a likeness to the Sididse. The way in which the animal uses its powerful liml)s is not 

 known, it never having been observed in the living state. 



1. Cytherella scotica, Brady. (Plate XXXIV. figs. 18-21.) 

 Cytherella Scotica, Brady, Brit. Assoc. Report, 1866, p. 211. 



Valves, as seen from the side, rather obliquely subelliptical, almost equal in height 

 throughout ; greatest height equal to more than half the length ; extremities broadly, the 

 posterior obliquely rounded, superior and inferior margins slightly concave in the middle. 

 Outline, as seen from above, subconical, subtruncate behind, obtusely pointed and slightly 

 emarginate in front ; greatest width situated near the posterior extremity and equal to 

 rather less than half the length, lateral margins nearly straight and converging gently 

 towards the front ; hinge-line slightly flexuous near the front, and sulcate. Surface of 

 the shell smooth, faintly punctate, more especially towards the posterior extremity. 

 Colour whitish, opaque. Animal unknown. 



Length in. . >■% «-vv-s. 

 Hab. The Mincli [Mr. Jeffreys' s dredgings), 60 fathoms. 



Two or three specimens only of this interesting species have occurred to the Eev. 

 A. M. Norman and myself, amongst sand dredged off the Scotch coast by Mr. Jeffreys. 

 It is very nearly allied to Cytherella ahyssonim, Sars ; and, indeed, until I saw specimens 



VOL. XXVI. 3 s 



