BRITISH DIATOMACEjE. 89 



S. Brightwellii (Synop. pi. ix. 69), which M. De Brebisson was at first 

 disposed to regard as identical with this species, is distinguished from it by its 

 coarser and more prominent costse and distinct striae. The outline of both 

 species is nearly alike ; 8. Crumena is, however, a smaller and more orbicular 

 form. 



27. Tryblionella levidensis, n. sp. V. linear, subacute at the 

 extremities; canaliculi very distinct, parallel, extending to the 

 central line, 5 in -001". Length of frustule -0012" to -0017". v.v. 



Brackish water. Cork City Park, April 1855, W. Sm. 



28. Tryblionella constricta, Greg. V. fiddle-shaped, apiculate ; 

 canaliculi obsolete ; striae delicate, 40 in '00 1". Length of frustule 

 •0008" to -0011". v.v. 



Greg. Mic. Journ. vol. 3. pi. iv. 13. T. Soleiformis, W. Sm. MSS. 



Marine. Stomach of Pecten, Coast of Sussex, Feb. 1853, and Kinsale Bay, 

 April 1855; Poole Bay, Sept. 1849; Cork Harbour, Aug. 1855, W. Sm. 

 Glenshira Sand, Dr. Gregory ; communicated by Dr. Arnott, March 1855. 

 (Near Marseilles in the Mediterranean, May 1854, W. Sm. Ceylon, Dr. Ke- 

 laart.) 



The surface of the valve in this species is striated as in Pleurosigma angu- 

 latum : the form is precisely that of Cymatopleura apiculata. 



29. Nitzschia Palea, W. Sm. F. V. linear; valve linear-lanceolate 

 with acute extremities. Length of frustule "0008" to '0016". v.v. 



Synedra Palea, Kutz. Bacill. iii. 27, iv. 2. Synedra Fusidium, Kiitz. Bacill. 

 xxx. 33. ad specimina authentica quae misit cl. De Brebisson. 



Freshwater: not unfrequent. Lewes, April 1853, &c, W. Sm. Haver- 

 fordwest, Oct. 1855, Mr. Okeden. (Avignon, May 1854, W. Sm. Falaise, 

 M. De Brebisson.} 



My specimens from Avignon, named S. Palea by M. De Brebisson, corre- 

 spond with authentic specimens of S. Fusidium from Falaise, sent by the same 

 kind friend. 



30. Nitzschia linearis, // '. Sm. 



Var. /3. Valve elliptical-lanceolate. Length of frustule -0018" to -0031". v.s. 



Fresh water. Derbyshire, Aug. 1853, Dr. Redfern. 



A common variety ; probably the earlier condition of the frustule. 



31. Nitzschia curvula, W. Sm. F. V. linear, tapering towards the 



