438 DIATOMACEiE. 



Frustulia viridis Kiitzing, Linntea, 1833, p. 551. Navicula 

 viridis Ehr., Die Infus. p. 182. t. xiii. f. 16. t. xxi. 

 fig. 12. Frustulia viridis Jenner, in Fl. of Tunbridge 

 Wells, p. 203. Nav. biceps ? Bory, Encyc. Meth. 11824. 



Hah. Frequent in Sussex : Mr. Jenner. Cheshunt : 

 A. H. H. Aberdeen : Dr. Dickie. Ireland : Mr. Moore. 



This is one of the finest and most beautiful of all the 

 Diatomacece, In young specimens the frustules are not at all 

 or scarcely inflated in the centre. 



86. SUKIRELLA Turp. 



Char. Frustules large, solitary, quadrangular ; angles -pro- 

 duced, striated. 



Derivation. Named in honour of Dr. Siiriraz/. 



This seems to be a well-marked genus. To it should be 

 referred, in addition to the two species described below, 

 Navicula? splendida, N. ? undulata, N. ? constricta, which would 

 stand thus : Surirella splendida, S. constricta, and ^S*. undulata. 

 The two latter species differ from all the others in the trans- 

 verse strias being in single and not double series, that is, they 

 pass entirely across the frustule. This genus seems to have 

 been indicated by Ehrenberg. 



1. Surirella biseriata Breb. 



Plate CII. Fig. 1. 



Char. Frustules in front view quadrangular, about three 

 times as long as broad, icith straight sides and truncate ex- 

 tremities ; in lateral aspect oval, with pointed ends. 



Navicula? hifrons Ehr., Die Infus. p. 186. t. xiv. fig. 2. 



Sui^irella biseriata Jenner, in Fl. of Tunbridge Wells. 

 Hab. Ashdown Forest, Piltdown Common, Broadwater 



Forest, and Warbleton : 3Ir. Jenner. 



