24 BRITISH DIATOMACEiE. 



Genus 7. EUPODISCUS, Ehr. 



Frustules free or adherent, disciform ; valves convex ; disc with 

 elevated processes. 



Closely allied to the last, but differing from it in the less distinctly 

 cellular structure of the valve, which in some species is wholly absent, 

 and in the presence of the horn-like processes of the disc, which do 

 not occur in Coscinodiscus. It differs from Genus 10. in its orbicular 

 form and in the horns springing directly from the surface of the valve, 

 while in Triceratium they are confined to the angles and are formed 

 by the prolongation of the latter. 



1 . Eupodiscus Argus, Ehr. Cells of V. irregular in outline, pro- 

 cesses three or four. Diam. "0065" to '01 13". v.s. 



Kiitz. Bacill. i. 6. E. Gennaniciis, Kiitz. Sp. Alg, p, 134. Prit. Anim. 

 xiv. 41. 



Marine or brackish water. Thames near Gravesend, Mr. Poulton. Near 

 Faversham, Mr. Shadbolt. River Orwell near Ipswich, Mr. Hodgson. 



Plate IV. 39. 



2. Eupodiscus fulvus, n. sp. Cellular structure indistinct, radiate ; 

 colour of dry valve tawny. Diam. -0018" to -0028". v. v. 



Marine. Poole Bay, Sept. 1851, W. Sm. 

 Plate IV. 40. 



3. Eupodiscus crassus, n. sp. Cells circular; V. somewhat opaque ; 

 colour of dry V. purplish ; margin smooth. Diam. '0011 to "0021. 

 v.v. 



Marine. Poole Bay, 1848, W. Sm. Near Ipswich, Mr. Hodgson. 

 Plate IV. 41. 



4. Eupodiscus radiatus, Bail.} Cellular structure of V. distinct; 

 cells circular ; processes four, radiate, two larger than the others, 

 v.s. 



Marine. Detected by 3Ir. West among other Diatomacese from the rivers 

 Orwell and Thames. 



Supp. Plate XXX. 255. 



