BRITISH DIATOMACE.E. 37 



2. Cymatopleura apiculata, n. sp. V. fiddle-shaped, apiculated; 

 undulations about four. Length '0021" to '0051". v.v. 



C. Solea, W. Sm. Ann. 2nd Ser. vol. vii. pi. iii. 8. 



In numerous localities with the former. I am not certain that the present 

 is entitled to rank as a distinct species ; it is usually much smaller than the 

 former and of a more rounded outline, but intermediate specimens sometimes 

 occur, and in Ehr. Inf. xiii. 22. fig. 2, copied in Prit. Anim. pi. iii. fig. 155, 

 we have a form as large as SoJea with distinct apicula as in the present species. 



Plate X. 79. 



3. Csrmatopleura parallela, n. sp. V. linear, extremities attenuate, 

 obtuse. Length -0021" to -0048". 



Fresh water. Iford near Lewes, Oct. 1852, W. Sm. 

 Supp. Plate XXX. 263. 



4. Cymatopleura elliptica, TF, Sm. V. broadly elliptical, some- 

 what acuminate, with four or five undulations ; surface obscurely 

 striated. Length -0016" to -0055". v.v. 



Stirirella elliptica, Bre'b. in Kiitz. Spec. Alg. p. 37. ad specimina quae com- 

 munica^it cl. De Brebisson, Aug. 1852. W. Sm. Ann. 2nd Ser. vol. vii. 

 pi. iii. 10 & 11. Prit. Anim. xviii. 7. 



Fresh water: frequent. River Frome, May 1849. Plumpton, Sussex, 

 April 1852. Guildford, Mi'. Capron, &c. &c. The larger variety in Lough 

 Mourne and Peterhead Deposits, Dolgelly Earth, &c. 



Plate X. 80. 



5. Cymatopleura Hibemica, JV. Sm. V. orbicular, with prominent 

 subacute extremities; undulations three; striae obscure. Length 

 •0022" to -0052". v.s. 



W. Sm. Ann. 2nd Ser. vol. vii. pi. iii. 12. 



Fresh water. Lough Neagh, Co. Antrim, Dr. Dickie. River Bann, Mr. 

 Cocken. 



Plate X. 81. 



Genus 16. NITZSCHIA, Hass. 



Frustules free, elongated, compressed ; valves linear, keeled, with one 

 or more longitudinal lines of puncta ; keel frequently eccentric. 



This genus embraces a large luimber of species, differing in form 



