BRITISH DIATOMACE.E. 41 



Sect. IV. Valves arcuate. 



12. Nitzschia Amphioxys, W. Sni. F. V. linear, quadrangular; 

 V. elliptical-lanceolate, arcuate, with acute and somewhat promi- 

 nent extremities; striae distmct, 30 in '001". Length -0016" to 

 •0043". v.v. 



Eunotia amphioxijs, Kiitz. Bacill. xxix. 44, xxx. 1. 

 Freshwater: cominon. Lewes, Jan. 1851, W. Sin. 

 Plate XIII. 105. 



13. Nitzschia vivax, n. sp. F. V. linear; V. hnear lanceolate, ar- 

 cuate, extremities produced into a prominent beak; striae distinct, 

 30 in -001". Length -0026" to -0056". v.v. 



Fresh or slightly brackish water. Near Lewes, Oct. 1852, W. Sin. 

 Supp. Plate XXXI. 267. 



14. Nitzschia parvula, n. sp. V. with central constriction, puncta 

 obscure, extremities pi'ominent; strice faint, ^0 in 'OOl". Length 

 •0012" to -0015". v.v. 



Marine : encrusting a sponge, Poole Bay, Nov. 1849, W. Sin. 

 Plate XIII. lOG. 



15. Nitzschia minutissima, W. Sin. V. linear; puncta distinct, 

 with prominent and acute extremities ; strioe obscure, 72 in 'OOl". 

 Length -0008" to -0011". v.v. 



Synedra dissipata, Kutz. Bacill. xiv. 3. xxx. 53. ad specimina quae misit el. 

 De Brebisson, Sept. 1852. 



Fresh water: on chalk rocks. Near Beachey Head, April 1852, W. Sm. 



Plate XIII. 107. 



Sect. V. Valves constricted. 



16. Nitzschia dubia, JF. Sm. F. V. elliptical, slightly constricted 

 towards the centre, and tapering towards the somewhat truncate 

 extremities ; keel very eccentric ; V. obscurely striated ; strife 60 

 in -001". Length -0042" to "0066". v.v. 



/3. A smaller form. 



