252 Prof. Jones 8f J. W. KirJcby — Carboniferous Ostracoda. 



the species is more nearly related to Cytherella 1 than to Leper ditia. 

 To that genus then we refer it ; and in doing so we consider that 

 the convex edge is the back, thus bringing the large valve to 

 the right hand, and the more compressed or narrowest half of the 

 carapace to the front as the anterior portion, and so have it in 

 harmony with what is to be observed in other Cytherella}. 



From the Gayton specimens we give the following provisional 

 description, with the intention of noticing the species more fully on 

 another occasion. 



Carapace subovate in outline ; dorsal margin arched and highest 

 about the posterior third ; ventral margin straight or faintly 

 incurved ; extremities rounded, the posterior obliquely so ; the 

 hinder third much higher than the anterior ; the carapace is tumid 

 and high behind, compressed and low in front. The left valve is 

 much smaller than the right ; not much more than half as high as 

 long, while the right is two-thirds as high as long ; the right valve 

 overlaps the left round the whole of its margin. Viewed from above 

 the profile of the carapace is subovate, widest behind, pointed in 

 front. End view oval. It is rather thick-shelled : the surface is 

 smooth. Length -gV inch. 



The only other English locality for this species is Skellygate, 

 Northumberland, where it occurs in a shale of the Lower-Carboni- 

 ferous Series. 



6. Cytherella attenuata, Jones and Kirkby. Plate VII. Figs. 

 14a, 146, 14c. 

 Leperditia attenuata, J. and K. 1880, Quart. Journ. Geol. Soc. vol. xsxvi. p. 588. 

 One or two examples of another form, also formerly referred by 

 us to Leperditia, occur with the other specimens from Gayton. It is 

 often found along with G. extuberata in Fife, and, like the latter, it 

 probably belongs to Cytherella. Indeed, we are not sure that the 

 relationship may not be closer to the species just described, for it is 

 possible that the differences observed may be due to sex. These 

 differences consist chiefly in the somewhat neater form of attenuata, 

 in the less strong (though still complete) overlap of the right valve, 

 and in the lateral contour, when seen from above, being more 

 regularly lenticular, the ends being almost alike, and the greatest 

 diameter being near the centre. In this latter character it certainly 

 looks very different from C. extuberata, and for the present we leave 

 it a distinct species. 



There are thus six recognizable forms, or species, among the 

 Ostracods from the Gayton Boring, namely — 



Eirkbya variabilis, sp. nov. Macrocypris Jonesiana (?), K. 



K.plicata, J. and K. Cytherella extuberata, J. and K. 



Bythocypris sublunata, J. and K., MS. C. attenuata,}. and K. 



Five of these were previously known to us from other localities ; 

 and one, which is the most abundant, is new. Of the former, all of 

 them are essentially Lower-Carboniferous forms, being most coni- 

 1 See Monogr. Carbonif . Entom. Pal. Soc. 1884, p. 58. 



