96 BRITISH DIATOMACE^l. 



55. Pinnularia nodosa, W. Sm. Valve with three subequal infla- 

 tions; extremities subcapitate, produced; striae marginal, 18 in 

 •001". Length of valve *0018" to -0025". Breadth at inflations 

 •0004" to -0005". v.v. 



Navicula nodosa, Ehr. Inf. xiii. 9. Kiitz. Bacill. xxviii. 81. Greg. Mic. Journ. 

 vol. 4. pi. i. 5. 



Fresh water. Elchies, Bamffshire, August 1854, Prof. Kelland. (Puy du 

 Capucin, Mout Dore, elev. 4567 feet, June 1855, W. Sm.) 



56. Pinnularia interrupta. Synop. xix. 184. 

 Var. /3. Costse not interrupted, v.v. 



Pinnularia biceps, Greg. Mic. Journ. vol. 4. pi. i. 28. 



Fresh water. New Forest, Hampshire, September 1854 ; Co. Cork, fre- 

 quent, &c, W. Sm. Fell-end, Lancashire, August 1854, Mr. Johnson. Haver- 

 fordwest, July 1855, Mr. Okeden. 



The absence or presence of the costse at the centre of the valve appears to 

 be an accidental circumstance, as numerous frustules may be found in which 

 the interruption is more or less complete. I cannot therefore at present admit 

 Dr. Gregory's new species P. biceps, the specific name of which is still further 

 inadmissible, having been appropriated to a very different form, viz. Navicula 

 biceps, Ehr. 



57. Pinnularia Integra, W. Sm. Valve elliptical-lanceolate, with 

 a slight subterminal constriction and linear produced apices ; striae 

 indistinct, 36 in -001". Length of valve -0008". Greatest breadth 

 of valve -0004". v.s. 



Pinnularia rostrata, Greg. Mic. Journ. vol. 4. pi. i. 14. 

 Fresh water. Powmouth, Ayrshire, July 1854, Br. Arnott. 



Owing apparently to a central and transverse inflation of the frustule, the 

 striee are more distinct and distant at the middle portion of the valve. 



The necessity of avoiding confusion in the syno^^my of genera so closely 

 allied as Navicula and Pinnularia, and the appropriation of the specific name 

 rostrata to Navicula rostrata, Ehr. in Kiitz. Bacill. iii. 55, necessitate the 

 rejection of an appellation otherwise appropriate and descriptive. The term 

 integra is designed to imply, that the appearance of a stauros, when the ends 

 of the valve are out of focus, is deceptive, and that the striee are truly con- 

 tinuous over the entire length of the valve. 



58. Pleurosigma transversale, W. Sm, Valve on S. V. elliptical- 

 lanceolate; extremities obtuse, occasionally slightly produced; 



