438 DIATOMACE^. 



Frustulia viridis Klitzing, Linniea, 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 : 

 C)^ A. H. H. Aberdeen : Dr. Dickie. Ireland : Mr. Moore. 



^^ </ll ' 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 Turjj. 



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

 duced, striated. 



Derivation. Named in honour of Dr. Suriray. 



This seems to be a well-marked s^enus. To it should be 

 referred, in addition to the two species described below, 

 Navicida? sjAendida, 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 strine 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 Breh. 



Plate CII. Fig. 1. 



Char. Frustules in front view quadrangular, about three 

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

 tremities ; in lateral aspect oval, witli pointed ends. 



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

 Surirella biseriata Jenner, in Fl. of Tunbridge Wells. 



Hab. Ashdown Forest, Piltdown Common, Broadwater 

 Forest, and Warble ton : 3Ir. Jenner. 



