BRITISH DESMIDIEiE. 103 



differs from tlie inflation of Cosmarlum ornatnm and C. commissurah, in 

 which plants it is longitudinal, and extends to or heyond the end margin. 



From all except Cosi/iariian Bi-oomeii, this species is known by its qua- 

 drangular segments, the lateral margins of which are sloi)ed, not rounded. 

 From that species it differs in its larger size, more distinct angles, and the 

 greater comparative length of the end margin, which is also convex and 

 slightly angular, whilst in C. Broomeii it is nearly straight. 



Length of frond -3^3^ of an inch ; breadth at constriction - ^ 3'^ g ; breadth of 

 segment -^\-^. 



Tab. XVI. fig. 5. a. Sussex specimen ; b. empty frond of French specimen ; 

 e. end view. 



19. C. Broomeii (Thwaites) ; segments compressed, minutely gra- 

 nulate, quadrilateral ; end view slightly inflated at the middle. 



Cosmariiim Broomeii, Thwaites, in lit. cum specim. (1846). 

 In brackish water at Sliirehampton near Bristol, Mr. Broome and Mr. 

 Thwaites. Piltdown, Sussex, Mr. Jenner. 



Frond as large as that of Cosmarium margaritiferum, deeply constricted at 

 the middle, the constriction forming a linear notch on each side. The seg- 

 ments are compressed, minutely granulate, quadrilateral, and twice as broad 

 as long ; the end margin is straight. 



The end view is twice as long as broad, slightly inflated at the middle and 

 broadly rounded at the ends. In the transverse view the inflation is greater, 

 and there is a slight constriction between it and the ends. 



Cosmarium Broomeii resembles in the front view some states of C. marga- 

 ritiferum, but differs in the end one. The inflation does not project at the 

 margin in the front view, as in C. ornatum, and the lateral margins are less 

 rounded, the pearly granules are also smaller. 



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

 striction Yxo" '■> thickness at the inflation in end view gi^- ; least thickness in 

 the end view yttT' Diameter of sporangium -5^. 



Tab. XVI. fig. 6. a. frond with endochrome ; b. empty frond ; c. end view; 

 d. transverse \aew. Tab. XXXII. fig. 7. sporangium. 



20. C. calatum ; frond suborbicular ; segments crenate, rough 



with pearly granules ; end view slightly inflated at the middle. 



Near Machynlleth, North Wales, /. R. Tunbridge Wells and AshdowTi 

 Forest, Sussex, Mr. Jenner. 

 Falaise, Brehisson. 



Frond nearly orbicular, scarcely so large as that of Cosmarium margari- 

 tiferum, compressed, constricted at the middle, the constriction causing a 

 linear notch on each side. The segments are scolloped or broadly crcnate : 

 each segment has six crenatures, four at the end, one at each side and one at 

 each intermediate angle, the lateral ones being the largest, whilst between all the 



