80 BRITISH DIATOMACE.E. 



acute. Length of frond 1". Length of frustule -0009". Breadth 

 of valve -00015". v.s. 



Marine. Tor Abbey Rocks, April 1842, Mrs. Griffiths. 

 Plate LIX. 372. 



Genus 57. HOMCEOCLADIA, Ag. 



Frond filiform, sparingly divided ; frustules nitzschoid, usually some- 

 what fasciculated ; striae obscure. 



The structure of the frustules, which is that of the genus Nitzschia, 

 separates the present from the other genera of the tribe. The species 

 are all marine, and appear to be rare, as few British localities are 

 known to me, or have been given by former authors. 



1. Homoeocladia Martiana, Ag. Frond simple, or dichotomously 

 divided, rugose; height of frond *3" to '7"; frustules usually in 

 dense fascicles, on F. V. linear-lanceolate, obtuse; V. linear, obtuse. 

 Length of frustule '0120". Breadth of valve -0002". v.s. 



Ag. Consp. p. 25. ad sp. authen. in herb. Grev. Kiitz. Bacill. xxx. 83. Sp. 

 Alg. 98. Prit. Anim. xvii. 47-49. Homoeocladia Anglica, Ag. Consp. 

 p. 25. Kiitz. Bacill. xxx. 82. Ralfs, Ann. 1st ser. vol. 16. iii. 1. 

 " Wrongly described in the ' Annals ' as H. Anylica" cl. Ralfs, in lit. 

 Nov. 1852. 



Marine. Torquay, Mrs. Griffiths. Ilfracombe, Sept. and Oct. 1 844, Mr. 

 Raffs. (Coast of Normandy, M. Be Brebisson.) 



A rare form, which has been described, as will be seen above, under the 

 two designations of Anglica and Martiana ; the specimens which I have seen 

 thus variously marked all belong to one species, and I have Mr. Ralfs' author- 

 ity for referring his H. Anglica to the older designation of Agardh. 



Plate LV. 347. 



2. Homoeocladia filiformis, n. sp. Frond linear, simple; fascicles 

 containing three or four frustules ; height of frond # 2" to # 3" ; F. V. 

 linear-lanceolate, obtuse ; V. linear-lanceolate, somewhat acute. 

 Length of frustule -0043". Breadth of V. -0003". v.v. 



ft. A smaller form. Length of frustule -0018". Breadth of V. -0002". v.v. 



Brackish water. Bexhill, Sussex, Sept. 1850; ft. Near Lewes, Aug. 1852, 

 W.Sm. 



Plate LV. 348. Var. ft. Plate LV. 348 ft. 



