RECENT BRITISH OSTRACODA. 



403 



Lucid spots about eight in number, subquadrangular, and arranged in two irregular 

 transverse rows. Two small shining eye-tubercles. Superior antennae robust, five- 

 jointed, second joint short, not much more than equal in length to the two succeeding ; 

 last joint short; terminal spines strong, curved. Inferior antennae robust, last joint 

 short and truncate, terminal claws rather short and slender; urticating seta reaching 

 to about the apex of the limb, equal in the male and female ; penultimate joint, in the 

 male, deeply emarginate about the middle of the posterior margin and bearing three seta), 

 one of which is short and slender, the central one longer and strongly pectinate, the other 

 very short and club-shaped (see Plate XXXIX. fig. 36). This arrangement is similar in 

 the female, but all the parts are feebly developed. Second joint of the last foot not much 

 longer than either of the two succeeding joints. Terminal claw long and strong. Abdo- 

 minal lobes truncate, each bearing two ciliated terminal setae. Eyes two. Basal portion 

 of the male copulative organs very large, quadrate ; apex acute and tapering. 

 Length 2V in., height -5-0 in. 



Hab. Littoral and in moderate depths up to 15 fathoms. In shell-sand from Walton and Whitstable 

 [Prof. T. Rupert Jones) ; Orkney, Girdler sand (Thames), Margate, and Cork {Mr. E. C. Davison) ; 

 Shetland, Loch Carron, Arran (N.B.), Tobermory, Youghall, Exmouth, Burrow Island, Guernsey, 

 dredged and living in tide-pools {Rev. A. M. Norman) ; Isle of Man, at roots of Laminarise, and 

 Cumbrae, Macduff, and Peterhead (Mr. D. Robertson) ; Aberdeenshire coast {Mr. Dawson) ; Galway, 

 Roundstone, and Birterbuy Bay (dredged), and abundantly in rock-pools at Arranmore, and on the 

 Dui'ham coast, and in sheU-sand from the Mumbles and Stranraer (G. S. B.) ; Norfolk coast, dredged 

 {Mr. D. 0. Drewett) . 



The form described by Dr. Baird under the specific name alba (see fig. 38 a) seems to 

 be the young of Cythere alhomaculata. C. strigulosa, Heuss, is very closely allied to, 

 but (according to s|)ecimens named by M. Bosquet) not identical with the present species. 

 C. alhomaculata differs remarkably from most of those with which it is associated, in the 

 form and structure of the shell, the peculiar armature of the second antennge, and the 

 structure of the mandibular palp, the latter being quite similar to the form observed 

 in the following section, which includes the species usually classed under the genus 

 Cythereis. These differences, though important, do not seem so much so as to warrant the 

 formation of an independent genus for this species. It is probably the most abundant 

 and most widely distributed of the British marine Ostracoda, being found all round our 

 coasts from high-water mark to a depth of about 15 fathoms. Very remarkable is its 

 apparent absence from the Scandinavian and other shores of continental Europe ; for, 

 being a large and conspicuous species, it can scarcely have escaped detection by such 

 naturalists as have recently investigated this group*. Should further observation show 

 that its distribution is confined to the British Islands, it will be a most interesting, and 

 perhaps a unique example of a purely British species having attained almost a predomi- 

 nant position in its own district as to range and numbers. It occurs in the glacial clays 

 of this country, but I am not aware whether it has been found in those of Norway. 



* Since this was in the printer's hands, I have seen a few specimens dredged by Mr. D. Robertson off the coast of 

 Norway, and others from the Mediterranean. 



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