REPORT ON THE OSTRACODA. 149 



[PI. XXXV. fig. 2, a~d. a Carapace seen from left side, h from above, c from below, 

 d from front. Magnified 60 diameters.] 



Paradoxostoma, Fischer. 



Paradoxostoma, Fisclier, ALhandl. d. Kgl. bayerisden Akad. d. Wissenschafton, Ed. vii. (1855). 



Shell thin and fragile, smooth, shining, and having no definite structure ; valves 

 subequal, mostly much higher behind than in front, usually elongate-ovate. Muscle- 

 spots as in Sclerochilus. Hingement simple ; ventral margins emarginate in front, so 

 that when the valves are closed there is still an elongated orifice through which the 

 suctorial mouth can be protruded. Anterior antennae extremely slender, six-jointed, and 

 armed with short setae ; posterior shorter and more robust, five-jointed ; flagellum large, 

 and almost as thick as the antenna itself. Poison-glands large, and mostly lobulated. 

 Mouth suctorial. Labrum and labium forming together a large and stout subconical 

 process projecting downwards, and terminating in a disk, with elevated margins, in the 

 middle of which is the orifice of the mouth. Mandibles very slender, protractile, 

 styliform, subulate at the aj)ex ; palp very slender and elongated, indistinctly jointed, 

 and without a branchial appendage. Terminal lobes of the first pair of jaws very narrow, 

 branchial plate elongate-ovate, and bearing at the base two deflexed setae. Feet short 

 and robust, last joint elongated, and bearing a very short, curved, terminal claw ; basal 

 joint of the first pair armed at the apex with a single strong spine. Postabdominal 

 lobes bearing two short hairs. One eye. 



Not many examples of this genus have been found in the Challenger dredgings, nor is 

 this to be wondered at, seeing that, in the British Seas at any rate, its members haunt 

 almost exclusively the littoral and laminarian zones. Foui-teen recent British species are 

 known to us, and Sars has described seven from Norway, some of which are identical 

 with British species ; eight species (two of which are rather dubious) have been recog- 

 nised in the British Post-Tertiary formations ; but from other parts of the world we have 

 no record of the occurrence of the genus, except in Dr Fischer's memoir, where one 

 species only [Paradoxostoma dispar) is described. The foreign gatherings which have 

 hitherto been described are exclusively from deep water ; when littoral gatherings 

 come to be examined, there can be no doubt that we shall have numerous examples of 

 Paradoxostoma. We may, indeed, expect, considering the beautifully marked shells of 

 many northern species, that among the sea-weed beds of the tropics wonderfully coloured 

 species may possibly abound ; the colouring of the shells of Ostracoda seeming to depend 

 very largely upon that of the plants amongst which they live, and on which, in all 

 probability, some of them, and especially Paradoxostoma, feed. 



It is not a little remarkable that one of the two species described in this monograph 

 {Paradoxostoma^ ensiforme) is from a European dredging, and is a well known European 



