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Part III. — Seventeenth Annual Report 



anterior one. Rostrum small. The antennules are very short, and 

 moderately setiferous — seven-jointed. The first joint is considerably 

 dilated ; the second, which is only about half the length of the first, is 

 also somewhat dilated. The third joint is nearly as long as the first. 

 The fourth joint — which is furnished with a moderately long asthetask — 

 and the last are of equal lengths, and are each as long as the second. 

 The fifth and sixth joints are somewhat smaller than the others (fig. 16, 

 PI. X.). These differences are more clearly shown by the formula 

 annexed — 



Numbers of the joints, 1 • 2 • 3 • 4 . 5 . 6 ■ 7 



Proportional lengths of the joints, 12 • 6 . 10 . 6 . 4 . 5 , 6 



Antennae small, three-jointed ; secondary branches very small, one-jointed 

 (fig. 18,P1.X.). The mandibles are also small; the mandible palp is obsolete, 

 being represented by a single small hair (fig. 19, PI. X.). The maxillae are 

 very small, the biting part is moderately broad, and armed with a few com- 

 paratively elongate teeth. The palp is a small cylindrical process, arising from 

 a moderately broad base, and furnished with a few hairs (fig. 20, PI. X.). 

 Posterior foot-jaws small. They somewhat resemble those of Cylindro- 

 psyllus Itevis (tig. 21, PI. X.). The inner branches of the first four pairs 

 of thoracic feet are all two-jointed, and shorter than the three-jointed 

 outer branches. The two joints that compose the inner branches are, in 

 each of the four pairs, more or less subequal, but those of the first pair 

 are rather stouter than the others. All the four pairs of feet are small 

 (figs. 7 and 8, PL XL). The fifth pair are minute. Each consists of a 

 small semicircular appendage bearing three or four small setae (fig. 9, 

 PI. XL). The caudal fume, which are small and cylindrical, are scarcely 

 twice as long as broad ; but each carries a long terminal spiniforni seta, 

 and also a few small hairs (fig. 11, PI. XL). 



The Male. — So far as can be made out, the male does not differ much 

 from the female, except that the antennules are modified for grasping, as 

 in other Harpactids. The fifth thoracic feet are also each provided with 

 an elongate and stout spine, in addition to the setae observed on the fifth 

 pair of the female (fig. 10, PI. XL). 



Habitat. — Brackish water-pools on the shore near Hunterston, Firth 

 of Clyde. Rather rare. 



Remarks. — This Copepod is somewhat like a Moraria or a Maraeno- 

 biotus in general appearance, as well as in some of the structural details \ 

 but it differs from these two genera, not only in the form of some of the 

 mouth organs, and of the fifth pair of thoracic feet, but in other details of 

 structure as well. Neither does it agree with Cylindropsyllus, although 

 it has a general resemblance to the members of that genus. For these 

 and other reasons, I have instituted for its reception the genus Lepto 

 caris (Greek — leptos, slender ; karis, a shrimp). 



Idya cluthw, sp. n. (PI. XIL, figs. 2-6). 



Description of the Female. — Length of the specimen figured, 1*1 7mm. 

 (■gL- of an inch). Somewhat like Idya furcata in general appearance, but 

 rather more slender (fig. 2). The antennules are moderately short ; being 

 only about two-fifths of the length of the thorax, they resemble generally 

 the antennules of Idya furcata, but the entire length of the first four 

 joints is proportionally shorter. The first four joints are sub-equal in 

 length ; the fifth is rather shorter than the one next to it ; while the 

 seventh is distinctly smaller than either the fifth or sixth (fig. 3). The 



