50 BRITISH DIATOMACE^E. 



Marine or brackish water. River Ouse near Lewes, July 1850, Sept. 1851, 

 W. Sm. Breydon, Norfolk, Mr. Bridgman. Thames mud, Mr. Roper. "Wis- 

 beach, Mr. S. Smith. Haverfordwest, July 1852, and Carmarthen, Sept. 

 1854, Mr. Okeden. 



Hitherto this species has only occurred to me in a dead state, and as 

 isolated frustules; but its form and structure are too near those of a Biddidphia 

 to permit its separation, and the filamentous condition of the species will no 

 doubt reward future explorers of the tidal harbours and estuaries of Britain. 



Plate XLV. 320. Plate LXI. 320. 



4. Biddulphia Baileyii, W. Sm. Valve imperfectly siliceous, with 

 two slight median elevations, each armed with one or two very long 

 awl-shaped spines ; processes somewhat linear towards the trun- 

 cate apices ; cellules in linear arrangement. Length of valve -0025" 

 to -0053". v.s. 



Zygoceros Mobilensis, Bail. Obs. 34 & 35 ? 



Marine. Poole Bay, July 1848; Stomach of Pecten, Coast of Sussex, 

 March 1854, W. Sm. Scarborough, Aug. 1854, Prof. Williamson. 



The present, if not identical with Prof. Bailey's species, is sufficiently near 

 to justify me in dedicating it to that excellent observer. 



Plate XLV. 322. and Plate LXII. 322. 



5. Biddulphia turgida, W. Sm. Valve elliptical, furnished with a 

 submarginal circlet of short abbreviated spines, and with two long 

 submedian awl-shaped spinous processes, together with the angular 

 processes, which are large, linear and truncate ; cellules distinct, in 

 linear arrangement. Length of valve "0035" to '0048". 



Cerataulus turgidus, Ehr. in Bail. Obs. fig. 25 & 2/. 



Marine. Newland near Haverfordwest, 30 feet below the surface, July 

 1854, Mr. Okeden. 



This fine species, which we owe to the patient enterprise of Mr. Okeden, has 

 not hitherto been found in Britain in a living state ; it appears, however, to be 

 so near the form figured by Prof. Bailey, that I have not hesitated to assume 

 their identity. The mode in which the specimens were procured, by means 

 of an apparatus especially constructed for the purpose, is described in an 

 interesting paper by Mr. Okeden in the Journal of Microscopical Science, 

 vol. .hi. p. 26. 



Plate LXII. 384. 



6. Biddulphia regina, n. sp. Valves with three median elevations, 



