CYTHEREIS WRIGHTII. 25 



4**** Cythereis ornatissima (Beuss), var. radiata, nov. (vel ornatissima-radiata). 



Plate IV, fig. 13. 



Lengtli, 1'04; height, '6 mm. 



The right valve of a weakly developed variety of C. ornatissima, without a 

 central boss and with very slightly indicated ventral ridge ; the reticulation passing 

 away, and leaving a local wrinkling of a few mesh-walls radiating from the centre 

 towards the border. On the mid-dorsal region a set of the mesh-walls of the 

 relatively faint reticulate ornament are strengthened so as to radiate upwards from 

 the middle of the valve towards the dorsal edge. Hinder margin smooth, and not 

 much depressed. 



Locality. — Greensand, Cambridge. Collected by Mr. G. R. Vine. 



4*****. C. ORNATISSIMA, var. stricta, nov. Plate I, fig. 63. 



Length '88, height '41 mm. 



A small Cythereis, with straight margins above and below ; neatly rounded 

 and denticulate in front; posterior margin depressed, and almost symmetrically 

 angular, below the truncated end of the suboblong body of the valve, which is 

 slightly wrinkled, and on which the subcentral boss and a subclavate lobe behind it 

 are distinct. The hinder margin is also denticulate on its ventral edge, as is 

 usual. 



At first sight this looks like an abnormal G. quadrilatera. One of Mr. 

 J. Wright's specimens from near Whiteabbey, Antrim, is like it; but relatively 

 short, subtuberculate on the body, and strongly toothed in front and behind. 



Locality. — CJialJc-mad, Didcot Station, Berks. 



5. Cythbeeis Wrightii, sp. nov. Plate IV, fig. 18. 



Length '8 ; height "46 mm. 



A unique, neat, small, subtriangular Cythereis, rounded in front, with a strong 

 and denticulate margin ; angular and somewhat dentate behind ; subcentral knob 

 very distinct ; dorsal edge bearing three or four distinct tubercles, and the ventral 

 ridge spinose. 



Locality. — Chalk, Keady Hill, co. Londonderry. Collected by Mr. Joseph 

 Wright; F.G.S., with whose name we associate it. 



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