28 BRITISH DIATOMACE/E. 



rarely constricted; striae moniliform, 20 in -001". Length of frus- 

 tule -0006" to -0028". Stipes never exceeding the length of the 

 frustule, solitary or subgregarious. v.v. 



Ag. Syst. p. 1. Ag. Consp. p. 59. Grev. S. C. F. pi. 295. Grev. B. F. 

 p. 404. Harv. Man. p. 199. Ehr. Inf. xx. 2. Prit. Anim. iv. 199-202. 

 Ralfs, Ann. vol. 13. pl.xiv. 9. ad specim. anthen. in Herb. Jenn. Raben. 

 Siissw. Diat. viii. 4. Echinella stipitata, Lyng. Tent. lxx. B. ad specim. 

 authen. in Herb. Grev. Achnanthes salvia, Kiitz. Bacill. xx. 5. et 

 A. intermedia, Kiitz. Bacill. xx. 6. ad specim. authen. quae dedit am. 

 De Brebisson. 



Marine or brackish water. Coast of Sussex, frequent. Pevensey, Sept. 1850. 

 Beachey Head, April ; Lancing, Aug. ; Bexhill, Oct. ; and Newhaven, Dec. 

 1852, W. Sm. Lancing, July 1843, Mr. Jenner. Torbay, Mrs. Griffiths. 

 (Mediterranean near Marseilles, and near Montpellier, May 1854, W. Sm.) 



An original specimen of Lyngbye's in the Herbarium of Dr. Greville enables 

 me to refer this species to Echinella stipitata, while the specimens received 

 from M. De Brebisson satisfy me that A. salina and A. intermedia of the 

 ' Bacillarien ' are also identical with the present. Some confusion appears to 

 have arisen from the fact that this species at one time forms a long filament, 

 and at another presents itself only in very short standard-shaped fronds ; no 

 distinction in the form or structure of the valve is however to be detected 

 between the two, and the varieties, if such they may be called, are often found 

 intermixed in the same gathering. Mr. Ralfs observes that " the lateral view 

 is more frequently constricted than in A. longipes," but my own observation 

 fails to confirm this. Usually the S. V. appears almost linear, becoming 

 rapidly attenuated towards the somewhat acute ends, and not unfrequently 

 the valve is inflated at the centre, assuming an oval outline, with the extre- 

 mities slightly produced : a slight constriction is no doubt occasionally to be 

 detected, but such an outline seems to me to form the exception rather than 

 the rule. 



Plate XXXVII. 301. Forming a long filament, Plate XXXVII. 301 /3. 



3. Achnanthes subsessilis, Kiitz. Filaments of few frustules, rarely 

 exceeding 4 ; valve elliptical, extremities rounded ; striae monili- 

 form, 24 in -001". Length of frustule -0013" to -0021". Stipes 

 very short, solitary, v.v. 



Kiitz. Bacill. xx. 4. Raben. Siissw. Diat. viii. 3. Ehr. Inf. xx. 3. Ralfs in 

 Ann. vol. 13. pi. xiv. 10. ad specim. authen. in Herb. Jenn. 



Fresh or brackish water : rare. Near Lewes, Oct. 1851, W. Sm. Scotland, 

 Dr. Greville. Pilling Marsh, Lancashire, Aug. 1852, Mr. Johnson. Wales, 

 Mr. Ralfs ; communicated by Mr. Jenner. 



Undoubtedly distinct from the last, with which it has sometimes been con- 



