BRITISH DIATOMACEiE. 57 



14. Pinnularia gracilis, Ehr. V. elliptical- lanceolate, attenuated 

 towards the extremities ; costae radiate, contiguous. Length •0016" 

 to -0022". vv. 



Navicula gracilis, Ehr. Inf. xiii. 2 ? Kiitz. Bacill. iii. 48 ? Navicula lan- 

 ceolata, Hass. Alg. cii. 14. 



Fresh water : frequent. Lewes, May 1850, W. Sm. Shalford, Mr. Capron. 



Plate XVIII. 174. 



15. Pinnularia viridula, W. Sm. V. elliptical-lanceolate, obtuse; 

 costae faint. Length -0006" to -0016". v.v. 



Navicula viridula, Kiitz. Bacill. xxx. 47? 



Fresh water. Kingston, Sussex, Nov. 1851, W. Sm. 

 Plate XVIII. 175. 



16. Pinnularia Cjrprinus, Eht'. V. elliptical, with a central infla- 

 tion ; extremities somewhat acute ; costae radiate, reaching central 

 line, subdistant, 18 in -001". Length -0016" to -0035". v.v. 



Ehr. in Kiitz. Bacill, xxix. 35 ? 



Marine. Belfast Bay, Aug. 1849, and Coast of Sussex, frequent, Sept. 1851, 

 W. Sm. Harwich, Mr. Shadbolt. 



Plate XVIII. 176. b. outline of F. V. 



17. Pinnularia divergens, n. sp. V. linear-elliptical, somewhat 

 attenuated towards the rounded extremities ; costae radiate at cen- 

 tre, afterwards divergent, absent from the middle of valve, sub- 

 distant, 11 in -001". 



Fresh water. Premnay Peat. Dolgelly Earth. 

 Plate XVIII. 177. 



18. Pinnularia stauroneiformis, W. Sm. V. elliptical; costee ab- 

 sent from the centre of V., not reaching the central line, contiguous, 

 30 in -001". Length '001 1" to -0025". v.v. 



Navicula Brebissonii, Kiitz. Bacill. iii. 49. xxx. 39. Sp. Alg. p. 72. ad specim. 

 quae dedit amicus De Brebisson. 



Fresh water. Lewes, Feb. 1852, W. Sm. Ben M'= Dhui, at an elevation 

 of 3000 feet, Mr. P. Grant. 



Plate XIX. 178. 



