220 Transactions of the Royal Microscopical Society. 



tity to have afforded means of estimating its variation ; in the type 

 form this variation is considerable. In a gathering from Sierra 

 Leone I found a frustule of the type form scarcely exceeding 

 ■0020" from angle to angle. 



Surirella contorta, n. sp., F. K. — Valve elHptically or slightly 

 ovate, canaliculi fine, numerous, alae inconspicuous, narrow median 

 elevation terminating in short sj)ines, surface of valve obscurely 

 striate, valve in f. v. contorted. Sub-peat deposit, Maunawata, 

 Welhngton, and Wangarei, Auckland, New Zealand. PI. LXXXL, 

 Fig. 4. This fine species of Surirella is undoubtedly distinct from 

 any form of this genus with which I am acquainted. The valves 

 in the Wangarei are more robust than those in the Mannawata 

 deposit, and of a yellowish brown colour, whilst those in the Man- 

 nawata material are hyaline, but differing in no other respect ; the 

 surface of the valve is blistered or puckered. The spines with 

 which the elevated ends of the median space terminate form a very 

 acute angle with the surface of the valve, and point in opposite 

 directions. 



I may here remark that the forms associated with the above are 

 those usually found in sub-peat deposits, viz. Epithemia, Navicula, 

 Himantidium, Cocconeis, Stauroneis, &c. Navicula ( = Pinnularia) 

 cardinalis is very fine in the Wangarei deposit, and differs from the 

 typical form in the greater distance of the costae and the broadly 

 cuneate ends. 



Stauroneis acuta is rare but fine in the above-named material. 



