72 BRITISH DIATOMACE^. 



Ill ponds : not uncommon. Lewes, Feb. 18.52, TV. Sm. 

 Plate XI. 92. 



The last four species are so closely allied, that it is difficult, by a verbal 

 description, to assign precise characters to each ; a close inspection of the 

 figures will assist in their discrimination, but it will probably be found neces- 

 sary, upon a further and wider examination, to unite some of those that I 

 have here felt myself obliged to separate. 



12. Synedra capitata, Ehr. V. linear, dilated towards the acute 

 extremities into a triangular head; striae 23 in 'OOl". Length 

 •0078" to -0185". v.v. 



Ehr. Inf. xxi. 29. Prit. Anim. iv. 185. Kiitz. Bacill. xiv. 19. Exilaria 

 capitata, Hass. Alg. xcvii. 1. 



Fresh water: common. Wareham, Sept. 1849, TV. Sm. Lough Moume 

 and Peterhead Deposits. 



Plate XII. 93. 



13. Synedra delicatissima, n. sp. V. elongated, very narrow and 

 gradually tapering to the somewhat acute extremities ; strice 27 in 

 •001". Length •0048" to -0092". v.s. 



Fresh water. Lough Neagh, Dr. Dickie, 1850. 

 Plate XII. 94. 



14. Synedra longissima, n. sp. V. much elongated, slightly and 

 gradually attenuated towards the inflated and obtuse extremities ; 

 striae 28 in •OOl". Length -0093" to -0183". v.s. 



Fresh water. Pond in Botanic Garden, Belfast, 1850, Dr. Dickie. 

 Plate XII. 95. 



15. Synedra tabulata, Kiitz. V. slightly tapering towards the some- 

 what inflated and obtuse extremities ; striae marginal, 27 in -OOl" ; 

 fi-ustules united into rectangular tablets. Length •0058"to '0087". 

 v.v. 



Kiitz. Bacill. xv. 10? 



Brackish water. Near Lewes, Sept. 1851, W. Sm. 

 Plate XII. 96. 



