6 Prof. W. Smith 07i the Diatomacese of the 



Dr. Gregory. Braemar, Aug. 1854, Br. Balfour. Var. y. Spring 

 at Chateau Vert near Marseilles. Braemar, Aug. 1854, Br. Balfour. 



Plate I. fig. 2 ^. Gomphonema capitatum, var. jS. Fig. 2 y. G. capi- 

 tatum, var. y. 



Gomphonema Brebissonii, Kiitz. Valve constricted above the 

 centre, upper extremity cuneatc, obtuse, lower gradually 

 attenuated and acute. Striae 24 in -001". Length -0013" 

 to -0018^'. v.v. 



Kutz. in Sp. Alg. p. 66. ad specim. authen. quae dedit am. De Brd- 

 bisson. 



Fresh water. Puy du Cliergue. 



But slightly differing from G. acuminatum, var. y, W. Sm. 

 Syn. Brit. Diat. pi. 28. 238. a"^ ; and probably only another va- 

 riety of the same species. 



Plate I. fig. 3. Gomphonema Brebissonii. 



Gomphonema elon^afum, W. Sm. Valves inflated at centre, 

 afterwards constricted towards both extremities, the upper 

 of which is capitate, or somewhat cuneate, the lower slightly 

 inflated below the constriction, afterwards attenuated and 

 obtuse. Strise 24 in -001'^ Length -0018" to -0045". v.v. 



Gomphonema Brebissonii, Greg, in Mic. Journ. vol. ii. p. 99. pi, 4. 18. 



Fresh water. Puy du Cliergue, W. Sm. Mull Deposit, Br. Gre- 

 gory. Wisbeach, April 1854, Mr. G. Smith. 



This may probably be a variety of G. Brebissonii, Kiitz., with 

 which it occurs intermixed in the French gathering ; both are 

 in my opinion closely allied to G. acuminatum. 



Plate I. fig. 4. Gomphonema elongatum. 



Diatoma vulgare, Bory. 



Var. p. Valve linear, extremities gradually and slightly at- 

 tenuated. Length of frustule -0018" to -0030". v.v. 

 Biatoma tenue, Ag., ad specim. in herb. Grev. 



Fresh water. Fountain in court of the Hotel des Colonies, Mar- 

 seilles ; Canal du Midi, and Canal de Crapone ; Plumpton, Sussex, 

 April 1852, W. Sm. Pentland Hills, April 1821, Br. Greville. 



The valve in the normal form of D. vulgare is elliptical and 

 suddenly attenuated towards the extremities. 



Plate L fig. 5. Biatoma vulgare, var. /3. 



Diatoma grande, W. Sm. Valve linear, constricted near the 

 capitate and rounded extremities. Costse 24 in '001". 



