Vol. 50.] EH^TIC AND LIASSIC 0STRAC0DA OF BRITAIN. 



165 



right valve (fig. 6 6) is narrower (less high) than the left (fig. 6 o), 

 and straighter on the ventral edge. 



Being strongly convex in the middle, and compressed at the ex- 

 tremities, especially in front, the edge-view of the carapace is broad 

 acute-oval (fig. 6 c). 



Surface smooth and shining ; the convexity of the right valve is 

 emphasized by a central swelling. 



This is to a great extent comparable with two species, undoubtedly 

 of Ct/theridea, from the Fuller's-earth Oolite, in plate ii. Proc. 

 Bath Nat. Hist. & Antiq. F. Club, vol. vi. (1889) pp. 264 & 265, 

 namely Gyikeridea obovata, J. & S., fig. 6, and C. subtrigona, J. & 8., 

 fig. 9 ; but it differs from both of them in some details, especially in 

 the edge-view. 



The specimens, of a reddish colour, some in a hard, and some in 

 a soft (weathered ?) limestone, probably from the Lower Lias of 

 either the Wainlode or the Westbury section (see pp. 156, 157), 

 were collected by the Eev. P. B. Brodie some years ago. 



Pigs. 6 a, 6, c, are reductions of drawings made by my friend 

 Mr. J. W. Kirkby from the curious, red-coloured, little carapaces, 

 in hard brownish limestone, probably (Mr. Brodie thinks) from 

 Wainlode. He has, however, had similar specimens from either 

 Hatherley or Westbury ; therefore the locality is uncertain. 



Besides the comparable forms noted above, there is a somewhat 

 similar species from the Lias of Antrim, which has been collected 

 by Mr. Joseph Wright, P.G.S., Belfast. 



There is a noticeable resemblance of the right valve (fig. 6 a) to 

 the woodcut, fig. 1, p. 11, Supplem. Monogr. Tert. Entom., Pal. 

 Soc. 1889, representing the outline of the right valve of Potamo- 

 cypris Brodiei, J. & S., from the Isle of Wight, but the latter is 

 much narrower and thinner. 



4. Cytheeidea Moorei, sp. 

 8 a, 8 b.) 



nov. (PI. IX. figs, la, 7 6, 7c, 





Length. 



Height. 



Thickness of carapace 



Fig. 7 « 



.. -65 



•35 



— mm. 



Fig. 7 6 



.. -65 



•325 



— mm. 



Fig. 7 c 



.. -65 



— 



*25 mm. 



Fig. 8 a 



. . -675 



•35 



— mm. 



Fig. 8 6 



. . -675 



— 



•3 mm. 



This has a shape modifications of which are common among 

 Cytherideai. Somewhat obovate, or subtrigonal with rounded ends ; 

 the front semicircular, the hinder extremity contracted and elliptic- 

 ally rounded ; the back slightly arched, and the ventral edge oblique ; 

 surface gently convex, glabrous, but minutely pitted ; the edge view 

 of the carapace lanceolate, acute in front, and somewhat rounded 

 behind. In exposures of the inside the edges are seen to be bevelled 

 within, and the dorsal edge shows some faint evidence of teeth. 



These are strong little valves and carapaces, almost black, congre- 

 gated in a bluish-grey marl from Beer-Crowcombe, Somerset (see 



