88 BRITISH DIATOMACEjE. 



22. Campylodiscus bicostatus, W. Sm. Valve suborbicular ; ca- 

 naliculi from twenty to thirty, interrupted, not reaching centre of 

 valve. Diameter -0015" to -0022". v.s. 



W. Sm. in Roper, Mic. Trans, vol. 2. pi. vi. 4. 



Marine. Thames mud, Mr. Roper. Breydon, Norfolk, July 1853, Mr. 

 Bridgman. Northfleet, Sept. 1854, Mr. Capron. 



23. Campylodiscus Clypeus, Ehr. Valve suborbicular ; canaliculi 

 from 40 to 100, irregularly interrupted, reaching over two-thirds of 

 the radius ; ridges of canaliculi, and two bands in centre of valve, 

 punctate. Diameter -0042" to -0098". v.v. 



Ehr. in Kiitz. Bacill. pi. ii. 5 ; in Prit. Anim. xii. 516. Microg. x. B. &c. 



Brackish water. Breydon, Norfolk, Sept. 1854, Mr. Wigham. Swansea 

 Dock, at the depth of 25 feet, Oct. 1854, Mr. Okeden. 



The last two species are closely allied, but an inspection of specimens of 

 both will satisfy any one of their distinctness. 



The occurrence of Campylodiscus Clypeus in a living state is an interesting 

 fact, as hitherto it has only occurred in deposits. 



24. Surirella apiculata, n. sp. Valve elliptical, ovate ; smaller ex- 

 tremity produced into a linear, truncate apiculum; canaliculi 15 in 

 •001". Length of frustule -0008" to -0012". v.v. 



Freshwater. Haverfordwest, April 1854, Mr. Okeden. Newhaven, Sussex, 

 Nov. 1854, W. Sm. 



A close ally, if not a variety of S. angusta. 



25. Surirella Amphioxys, n. sp. F. V. linear; V. elliptical-lan- 

 ceolate, extremities subacute ; canaliculi 9 in '001". Length of 

 frustule -0012". Breadth of valve -0005". v.v. 



Fresh water. Haverfordwest, August 1855, Mr. Okeden. 



26. Surirella Crumena, Breb. V. suborbicular; striae obscure; 

 canaliculi 15 in -001". Length of frustule -0009". Breadth of 

 valve -0008". v.v. 



Breb. in Kiitz. Sp. Alg. p. 38. 



Fresh water. River Avon, Lanarkshire, July 1854, Dr. Gregory. Near 

 Tantallon Castle, August 1854, Dr. Greville. 



