BRITISH DIATOMACE^E. 



Genus 36. EUCAMPIA, Ehr. 



Frustules cuneate, quadrangular or oblong, united into a spiral fila- 

 ment ; valves dotted, elliptical. 



The cuneate form of the frustules, and their development into a 

 spiral filament, ally the present genus with Meridion ; but the absence 

 of costae, with the broader form of the frustules and valves, place it in 

 close proximity to the last. Neither of the undermentioned species 

 have occurred to me in a living state ; but the structure of the frus- 

 tules, their presence with other familiar forms in a habitat exclusively 

 marine, and their similar behaviour under the action of nitric acid, 

 leave no doubt on my mind of their true Diatomaceous character, 

 and forbid their relegation to the family of the Desmidieae, a course 

 which has been adopted by Professor Kiitzing in apparent ignorance 

 of their true character and habitat. 



1. Eucampia Zodiacus, Ehr. Valve elliptical, with a deep central 

 excavation ; F. trapezoidal. Length of F. about '0014". v.s. 



Kiitz. Bacill. xxi. 21; Sp. Alg. p. 191. Prit. Anim. xiii. 43. 



Marine. Stomach of Pecten maximus. Coast of Sussex, Feb. 1853, and 

 March 1854, W.Sm. 



Plate XXXV. 299. Supp. Plate LX. 299. 



2. Eucampia Britannica, n. sp. V. plane ; F. oblong. Length of 

 F. about -0026". v.s. 



Marine. With the last, March 1854, W. Sm. 

 Supp. Plate LXI. 378. 



Genus 37. ACHNANTHES, Bory. 



Frustules geniculate, united into a filament, which is stipitate or 

 attached; valves striated, unsymmetrical, the lower with a longi- 

 tudinal and transverse line, and central and terminal nodules, the 

 upper with a longitudinal line only. 



The want of svmmetrv in the valves of their frustules is a character 



c3> 



<AR 



