92 BRITISH DIATOMACE.E. 



elliptical, extremities rounded ; striae 22 in -001". Length of V. 

 •0008" to -0016". Breadth of V. -0002". v.s. 



Breb. in lit. Oct. 1852, cum specim. 

 Brackish water. Saltcoats, Feb. 1854, andPowburn, July 185 4, Dr. Arnott. 



41. Navicula retusa, Breb. F. V. extremities truncate with rounded 

 angles ; V. linear, extremities rounded ; striae 16 in *00l". Length 

 of V. -0018" to -0022". Breadth of V. -0004". v.v. 



Breb. Diat. Cherb. fig. 6. 



Marine. Cork Harbour, Nov. 1855, W. Sm. 



42. Navicula Cocconeiformis, Greg. V. elliptical; extremities 

 subacute, or slightly produced and rounded ; striae indistinct, 54 

 in -001". Length of V. -0008" to -001 1". Breadth of V. 



•0004". v.s. 



Grev. Ann. 2nd ser. vol. 15. pi. ix. 6. Greg. Mic. Journ. vol. 4. pi. i. 22. 

 Fresh water. Braemar, August 1854, Dr. Balfour. 



43. Navicula elliptica, Kiitz.=N. ovalis, Synop. xvii. 153. 



Var. /3. Valve linear, or slightly constricted at centre, v.s. 



Fresh water. Lough Leven, June 1855, Dr. Gregory. 



The insertion of this interesting form affords me an opportunity of rectify- 

 ing the synonymy of N. elliptica and N. ovalis of the Synopsis, vol. i. p. 48. 

 M. De Brebisson informs me that N. elliptica, Kiitz. Bacill. xxx. 55, is a 

 freshwater form, first found by himself at Falaise ; that it is identical with my 

 JV. ovalis, and therefore claims priority over this latter, which must in con- 

 sequence be superseded. He suggests that the name N. ovalis should be 

 cancelled, and that the name N. Smithii be given to the marine species, which 

 I had designated N. elliptica : I gladly accept the compliment, and shall 

 make the correction in a future revision of the text. 



44. Navicula Amphisbsena. Synop. xvii. 147- 



Var. y. V. extremities scarcely produced, and subacute, v.v. 



Brackish water. Wisbeach, January 1854, Mr. S. Smith. Foundations of 

 Cleddan Bridge near Haverfordwest, July 1854, Mr. Okeden. 



