54 BRITISH DIATOMACE^. 



Genus 20. PINNULARIA, Ehr. 



Frustules free, oblong or lanceolate ; valves convex, with a median 

 line, and nodules at centre and extremities; ribbed or pinnated 

 with distinct costa; not resolvable into dots. 



The species in which the costae are absent from the centre of the valve, as 

 noticed at page 46, belong to Ehrenberg's genus Stauroptera, but the limits 

 of that genus are too indefinite to permit me to adopt it in the present work, 



1. Pinnularia nobilis, Ehr. V. linear, obtuse, with a central and 

 terminal inflation ; costae radiate, not reaching the median line, 

 contiguous, 12 in -001". Length -0112" to -0145". v.s. 



Navictda nobilis, Kiitz. Bacill. iv. 24. Sp, Alg. p. 80. ad specim. quae misit 

 amic. De Bre'bisson. Quek. H. C. pi. xii. 1. a. 



Fresh water. Lough IMourne Deposit. Dolgelly Earth. Premnay Peat. 

 Cantyre Peat. (Nova Scotia. Vermont, U.S.) 



Plate XVII. 161. 



2. Pinnularia major, W. Sm. V. linear, obtuse, with a central in- 

 flation ; costae as in the last, 14 in '001". Length -0072" to -0122". 

 v.s. 



Navictda major, Kiitz. Bacill. iv. 19. Navicula viridis, Ehr. Inf. xiii. 16. 

 Hass. Alg. cii. 2. 



Fresh water. Lough Mourne Deposit. Premnay Peat. Dolgelly Earth. 

 Mountains of Aberdeen, Dr. Dickie. Cantyre Peat. Peterhead anil Lough 

 Island-Reavey Deposits. 



Plate XVIII. 162. 



3. Pinnularia viridis, W. Sm. V. elliptical, attenuated ; costae as 

 in the last, 16 in -001". Length -0021" to -0068". v.v. 



/3. Costae parallel, absent from centre of valve. 



Navicula viridis, Ehr. Inf. xxi. 12. Prit. Anim. iii. 133-136. xviii. 1-6. Kiitz. 

 Bacill. iv. 18, 20. Quek. H. C. xii. 1. b. Navicula viridula, Ehr. Inf. 

 xiii. 17. 



Fresh water: very common. Wareham, Feb. 1848, W. Sm. Lough 

 Mourne, Lough Island-Reavey, and Peterhead Deposits. Premnay Peat. 

 Dolgelly Earth. Cantyre Peat'. (New Zealand, Nova Scotia, &c.) Var. /3. 

 Lewes, Mar. 1852, W. Sm. Ben M*^ Dhui, 3Ir. P. Grant. 



Plate XVIII. 163, Frustule with endochrome, Frontispiece, fig. CLXIII. 

 Var. /(3. PL XVIII. 163/3. 



