KNOWN SPECIES OF MARINE OSTRACODA. 363 
1. Jonesia stimMPpLEx, Norman. (PI. LVII. fig. 11, a—e.) 
Cythere simplex, Norman, Nat. Hist. Trans. Northumberland and Durham, vol. i. p. 17, pl. 5. 
figs. 1-4, 
Carapace compressed, elongated, rounded and narrowed in front, acuminate behind. 
Dorsal margin straight ; ventral margin bulging considerably behind ; the two margins are 
parallel for the greater part of their length, but converge suddenly and equally behind, 
forming an acuminate extremity. Anterior extremity narrowed, somewhat obliquely 
rounded. Viewed from above, the carapace is compressed, oblong oval, tapering at 
each extremity, subacute in front, pointed behind. nd view broadly ovate. Lucid 
spots about six in number; each spot linear-oblong and slightly curved, arranged in a 
parallel series, those in the middle being the longest, thus forming an oval patch placed 
in an oblique direction across the central portion of the shell. Surface smooth. 
Length 35 in. (1:27 mm.). 
Hab. Hunde Islands (Dr. P. C. Sutherland’s dredgings). Shetland, Dogger Bank, and 
Holy Island (Northumberland). Isle of Bute (Mr. D. Roberison). 
This species was very recently (1865) described by Mr. Norman from specimens 
taken on the Dogger Bank. The perfectly simple character of the hinge-joint does not 
allow of its being classed under any of the established genera ; and as it, in common 
with some other species, possesses further distinctive characters, I here propose for their 
reception the genus Jonesia, named after Professor T. Rupert Jones, whose valuable 
labours amongst the fossil Entomostraca need no further comment. In addition to the 
present species, Cythere contorta, Norman, and C. variabilis, Baird, may be noted as 
coming under the genus Jonesia. 
J. simplex is an exceedingly well marked species, and apparently very constant in its 
characters, there being little or no difference observable between the specimens from 
the various localities mentioned above. I have also seen fossil specimens collected by 
Mr. D. Robertson from the glacial clay of the Clyde district, which are in no respect 
distinguishable from the recent ones. The species figured by M. Bosquet (Crustacés 
Fossiles de Limbourg) as Cytheridea harrisiana, Jones, is either identical with, or very 
nearly allied to, the present species. The true Bairdia harrisiana, of which Mr. Jones 
has kindly allowed me to examine the type specimens, is an entirely different thing. 
Genus Bairpia, M‘Coy. 
Animal a Cythere (2). Carapace varying from a broadly triangular form with rounded 
or obtuse extremities, to a narrow, elongate, subtriangular form with somewhat acute 
extremities. Surface quite smooth, finely punctate, or occasionally setiferous; no 
central tubercle. Lucid spots mostly well marked. The right valve is much the smaller 
of the two, and its edge lies within, and on the dorsal margin is overlapped by, that of 
the left. The dorsal edge of the right valve is quite simple. Ventral margin incurved. 
3B 2 
