104 BRITISH DESMIDIE-iE. 



crenatures the margiii is somewhat suleated. The pearly granules are distinct, 

 especially on the crenatures, to which they give a dentate appearance. The 

 end view is slightly cruciform, and the transverse view still more so. The 

 lateral view is constricted at the middle and emarginate at the ends. 



Cosmariiim ccelatum is a very distinct species and requires no comparison 

 with any other. 



Length of frond from -^\^ to y^y of an inch ; greatest breadth from yo^ 

 to ^-i-g- ; breadth at constriction from ^^^3;^ to y-gV?"' 



Tab. XVII. fig. 1. a. frond with endochrome ; b. empty frond; c. empty 

 frond of Sussex specimen ; d. dividing frond ; e. side view ; /. end view ; g. 

 transverse view. 



21. C. ornatum (Ralfs) ; segments twice as long as broad, rough with 

 pearly granules which give a dentate appearance to the margin ; 

 inflation forming a truncate projection at the end ; end view cru- 

 ciform . 



Cosmarium ornatum, Ralfs in Annals of Nat. Hist. v. 14. p. 392. t. 11. f. 3 

 (1844); Trans, of Bot. Sac. of Edinburgh, v. 2. p. 148. t. 16. Jenner, 

 Fl. ofTimbridge Wells, p. 194. Hassall, Br. Alg. p. 364. 



Cosmarium Sport el I a, Brebissou, MS. 



Not uncommon. Dolgelley ; Barmouth ; and Penzance, J. R. Ashdown 

 Forest, &c., Sussex, and Weston Bogs near Southampton, 3Ir. Jenner. Ches- 

 hunt, 3Ir. Hassall. Kerry, Mr. Andreivs. Ben Muich Dhu (alt. 2800 ft.) ; 

 Linn of Dee (1190 ft.); Little Craigendall, Braemar, Aberdeenshire, Dr. 

 Dickie. Aberdeen, Mr. P. Grant. Ambleside, Westmoreland, Mr. Side- 

 botham. 



Falaise, Brebisson. West Point, New York, Bailey. 



The frond is generally smaller than that of Cosmarium margaritiferum and 

 deeply constricted at the middle ; the constriction forms on each side a hnear 

 notch, which is nearly closed by the apposition of the segments. The seg- 

 ments are compressed, about twice as broad as long, and rough with pearly 

 granules which give a dentate appearance to the margin. The inflation ex- 

 tends beyond the margin in a truncate projection, and in the end view forms 

 a rounded lobe on each side, prodvicing a cruciform figure. 



Cosmarium ornatum differs from the other species by its inflation extending 

 into a truncate projection beyond the margin. 



The sporangium has been found near Bristol by Mr. Broome, and I have 

 gathered it at Penzance. Its spines are elongated, slightly divided at the 

 extremity and dilated at the base. 



Length of frond -^\^ of an inch ; greatest breadth -^\^ ; breadth at con- 

 striction a-oTTJ diameter of sporangium -^\-g; length of spine of spo- 

 rangium T-sVa . 



Tab. XVI. fig. 7. a. front view of mature frond ; b. empty frond ; c. end 

 view ; (/. transverse view ; e, sporangium. 



