BRITISH DIATOMACE^. 2; 



Marine. Poole Bay, Aug. 1848. Hove, Sussex, Nov. 1852, very sparingly, 

 W. Sm. Folkestone, Sept. 1852, Mr. Capron. (Peruvian Guano.) 



Plate V. 45. Supp. Plate XXX. 45. 



3. Triceratium striolatum ? Ehr. V. with acute angles, not ele- 

 vated or produced ; cellular structure faintly discernible, v.s. 



Kutz. Bacill. xviii. 10? 



Brackish water. Near Lewes, Oct. 1850, W. Sm. I refer this doubtfully 

 to the species described and figured by Prof. Kutzing. 



Plate V. 4G. 



Genus 11. CYCLOTELLA, Kutz. 



Frustules free or adherent, disciform ; valves convex or plane, striated, 

 striae rayed. 



Closely allied to Coscinodiscus and Melosira, the absence of a cel- 

 lular structure separating it from the first, the shallow valve and non- 

 adherent frustule from the second. The undulations on the F.V. of 

 the species first described, which are by no means constant, are 

 probably due to an irregular depression in the centre of the valve, a 

 character which may be also noticed in the second species, but being 

 less strongly marked in the latter, and the outline being more regular, 

 the appearance of undulations is not so evident. 1 have also noticed 

 in the first species, that although no undulations may be discernible 

 in the dry frustule, they become apparent when the objects are im- 

 mersed in balsam. 



1. Cyclotella Kiitzingiana, Thiv. V. undulated; strise delicate, 

 extending over half the disc, at margin 20 in '001"; centre of V. 

 smooth. Diam. -0005" to 0015". v.v. 



/3. Valve without undulations. 



Thw. Ann. 2nd Ser. vol. i. pi. xi. d. C. operculata /3. rectangula, Kiitz. Sp. 

 Alg. p. 19. ad specimina quae misit cl. De Brebisson, Oct. 1852. 



Fresh or brackish water. Near Bristol, Mr. Thwaites. Warehara, Nov. 

 1848. /3. Lewes, Oct. 1850, W. Sm. Thames, Northtleet, Mr. Shadbolt, 

 Feb. 1851. 



Plate V. 47- h', Sporangial (?) frustule. Frustule with endochrome. Fron- 

 tispiece, fig. XLVII. 



