BRITISH DIATOMACE^. 19 



Genus 4. AMPHORA, Ehr. 



Frustules free, or adherent ; valves cymbiform, with a central marginal 

 nodule. 



The valves in this genus are exceedingly convex, closely resembling 

 those of Epithemia rupesiris, and the section of the frustule is the 

 same as that which I have described under that species. It is pro- 

 bable that most of the Amphora are at first adherent, but they are 

 usually found detached, and sparingly diffused among other Algae. 



1. Amphora ovalis, Kiitz. F. V. elliptical, internal margin of V. 

 inflated at the nodule; striae moniliform, distinct, 24 in '001". 

 Length -0012" to -0038". v.v. 



Kiitz. Bacill. v. 25 & 39. Nav. Amphora, Ehr. Inf. xiv. 3. Prit. Anim. 

 iii. 153. 



Fresh water: frequent. Lewes, April 1852, W. Sm. Lough Mourne De- 

 posit. Peterhead Deposit, &c. 



Plate II. 26. Frustule with endochrome, Frontispiece fig. XXVI. 



2. Amphora affinis, Kiitz. F. V, oblong, with round or truncate 

 extremities ; strite distinct, 27 in -001". Length -0016" to -0022". 

 v.v. 



Kiitz. Bacill. xxx. 66. 



Brackish water. Near Lewes, Sussex, Feb. 1852, W. Sm, 

 Plate II. 27. 



3. Amphora hyalina, Kiitz. F. V. elliptical, acute ; V. imperfectly 

 siliceous, longitudinally rugose; striae obscure. Length "0021" 

 to -0032". v.v. 



Kiitz. Bacill. xxx. 18. 



Brackish water. Coast of Sussex, Nov. 1850, W. Sm. Near Lancaster, 

 Mr. Johnson. 



Plate II. 28. 



4. Amphora salina, n. sp. F. V. elliptical, truncate, extremities 



c 2 



