BRITISH DIATOMACEifC. 35 



Genus 14. TRYBLIONELLA, IV. Sm. 



Frustules free, elliptical or linear; valves plane; alas subraarginal or 

 obsolete ; canaliculi inconspicuous, parallel. 



This genus differs from Campxjlodiscus in the more elongated form 

 of its frustules and the absence of the characteristic bend in its 

 valves ; the canaliculi are also more minute and parallel rather than 

 radiating. It agrees with Surirella in the presence of alee, but these 

 arise from the disc, and are not, as in Surirella, prolongations of the 

 margin. It is also distinguished by its less conspicuous canaliculi, 

 and by the frustule never assuming the cuneate form so notable in 

 Surirella. 



1. Tryblionella Scutellum, n. sp. V. elliptical, marked with a cen- 

 tral depressed line ; canaliculi obsolete ; alas very short. Length 

 •0058" to -0085". v.v. 



Surirella circumsuta, Bail. Obs. pi. ii. 36. ad specimina quse communicavit 

 Prof. Williamson. 



Marine. Poole Bay, Nov. 1848, JF. S^n. (Hudson River.) 



Plate X. 74. 



2. Tryblionella gracilis, n. sp. F. V. linear, attenuate towards the 

 extremities ; V. linear acuminate ; canaliculi parallel, extending to 

 the central line, 10 to 12 in -001"; alas distinct. Length -0023" 

 to 0075". v.v. 



Fresh and brackish water. Near Lewes, Dec. 1850, and Oct. 1852, TV. Sm. 

 Plate X. 75. Frustule with endochrome. Frontispiece, fig. LXXV. 



3. Tryblionella marginata, n. sp. F. V. inflated, extremities ob- 

 tuse; V. elliptical, acuminate; canaliculi distinct, marginal, 18 in 

 •001"; alae conspicuous. Length •OOll" to -0026". v.v. 



Fresh and brackish water. Near Lewes, Sept. 1851, TV. Sm. Pilling and 

 Cockerham Marshes, Lancashire, Mr. Johnson. Near Belfast, Dr. Dickie. 



Plate X. 70. Lleal section of frustule, PI. X. fig-*. 



D 2 



