100 BRITISH DIATOMACEiE. 



constricted near both extremities ; the upper slightly produced, 

 linear and truncate ; the lower somewhat capitate and obtuse ; 

 striae 20 in -001". Length -0012" to -0017". Greatest breadth of 

 V. -OOO.i". v.s. 



Greg. Mic. Journ. vol. 4. pi. i. 42. 



Fresh water. Lough Leven, September 1854, Dr. Gregory. 



69. Gomphonema insigne, Greg. V. lanceolate, upper extremity 

 rounded, lower subacute ; striae 20 in *00l". Length of F. -0016" 

 to -0025". Greatest breadth of V. '0005". v.s. 



Greg. Mic. Journ. vol. 4. pi. i. 39. 



Fresh water. Duddingston Lough near Edinburgh, April 1854, Dr. Greville. 

 Braemar, August 1 854, Dr. Balfour. 



The last two species are probably varieties of the same form. 



70. Gomphonema Fibula, Breb. F. V. slightly cnneate ; V. sub- 

 linear, constricted near the upper and larger extremity, which is 

 conspicuously capitate, obtuse at the lower; stipes abbreviated; 

 nodule obsolete ; striae 40 in -001". Length of F. -0016" to -0024". 

 Greatest breadth of V. -00025". v. v. 



Breb. in Kiitz. Sp. Alg. p. 65. ad specim. authen. 



Freshwater. Rackham Common, Sussex, August 1853, W.Sm. (Falaise, 

 M. De Brebisson.) 



The absence of a nodule and the abbreviated stipes would rather point to 

 Synedra as the genus of this form ; but the cuneate frustule is precisely that 

 of a Gomphonema. 



71. Gomphonema subtile, Ehr. Valve slightly inflated at centre, 

 gradually attenuated towards both extremities, the upper of which 

 is capitate and truncate, and the lower obtuse ; striae 26 in -001". 

 Length of F. -0018". v. v. 



Ehr. in Kiitz. Sp. Alg. p. 68. Microg. xvi. iii. 38, &c. Greg. Mic. Journ. 

 vol. 4. pi. i. 12. 



Fresh water. Lough Avaul, Co. Cork, June 1855, W. Sin. 



Doubtfully distinct from G. constrictum or G. acuminatum. First detected 

 as a British form by Dr. Gregory of Edinburgh, and said by him to occur in 

 two localities in Scotland. 



