RATTRAYELLA. 



49 1 



GENUS 153. RATTRAYELLA. DE TONI. 1889. 



life 



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mh 



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s^g. 



mmm ^%m 





S-3a 



i#s 



: 



Valves circular, plain in 

 the median portion, then 

 gently convex towards the 

 margin, very finely punctate, 

 with puncta arranged in 

 radiating lines and often 

 covered with a kind of 

 vague network. Margin 

 showing small processes, 

 rounded or elliptic, between 

 each of which is one or 

 two apiculi. 



This genus only comprises 



Fig. iT&.Rattrayella Oatr.arucnsis. a single species. B . Oamciril- 



ensis (Grun.), De Toni, found in the fossil deposits of Sysran, Simbirsk and 

 Ananino (Russia), as well as in the deposit of Oamaru. The figure in the 

 text (fig. 22S), is drawn from one of my photographs. 



GENUS 154. CESTODISCUS GREV.. 1865. 







Valves disciform, circular, oval, rarely angular, 

 granular, with granules arranged in radiating 

 rows, furnished with round or elongated tubercles, 

 forming a complete circle, near the margin of the 

 valve. 



Fig. 229. 

 Cestodiscus Pr 



This genus only comprises a small number o* 

 species, the greater part being fossil. I include in my 

 generic diagnosis Trkeratium cinnamomeum Grev., which should, perhaps, 

 form a special genus. 



The figure in the text (fig. 229), represents Cestodiscus Proteus Hard- 

 man, after an authentic example of the author. Mr. Rattray classes the 

 Cestodiscus, Perithyra, and Micropodiscus among the Coscinodiscus. 



