257 



Some of the species in this list have been described as new to 

 Britain by Mr Roper, in a late paper published in the Microscopi- 

 cal Journal. The Coscinodiscus, not named, seems from the de- 

 scription to be the same with that found at the mouth of the Thames, 

 and is an exceedingly beautiful disc. The four species of Actinop- 

 tychus are those described by Ehrenberg, and are new British species. 

 They exhibit the strong siliceous cellular tissue underneath the 

 moniliform structure of the surface, as in Actinocydus. The exam- 

 ples of Triceratium striolatum, and also Zygocerus rhombus, dif- 

 fered somewhat from the figures and descriptions given of them, 

 being provided with spines along the side, and with two spines placed 

 close to the projecting terminations or angles of the valve, and which 

 were always present in the examples that had come under observa- 

 tion. The surfaces of the valves were also seen to be dotted over 

 with small nodules, giving them a very remarkable appearance, and 

 which might be seen to project from the surface when the valve was 

 suitably placed ; these appearances might be attributable to a more 

 mature developing of the siliceous structure. 



