BRITISH DESMIDIEiC. 109 



V. 2. p. 1 j1. t. 16. Jenncr, FL ofTunhridge Wells, p. 196. Hass. Br. 

 Alff. p. 367. 

 Closterium clandesthnm, Kiitz. Phy. Germ. p. 132 (1845). (Kutzing in lit.) 



Rather common. Dolgelley ; near Lampeter ; and Penzance, J. R. Ash- 

 down Forest, Grcatham Bogs near Pulborough, Sussex ; and near Southampton, 

 Mr. Jenner. Near Bristol, Mr. Thwaites. Near Congleton, Cheshire ; and 

 Ambleside, Westmoreland, Mr. Sidebotham. Kerry, Mr. Andrews. 



Falaise, Brcbisson. Germany, Kutzing. ^ 



The frond is minute, subcylindrical, twice as long as broad, with a very 

 slight constriction at the middle, and rounded at the ends. The transverse 

 view is circular, with a large opening. 



Cosmarium Cucurbita agrees in size with C. cglindrieum, but is punctate, 

 not granulate. The segments differ also in figure from those of that plant, and 

 resembling two cupping-glasses with their mouths m contact, are aptly charac- 

 terized by the specific name. 



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

 striction YXTg. 



Tab. XVII. fig. 7. a. front view of mature frond ; b, c. empty fronds ; 

 d. transverse \'iew ; e. dividing frond. 



30. C. Thivaitesii ; frond cylindrical, constricted at the middle 



and rounded at the ends ; puncta very indistinct. 



Bristol, Mr. Thwaites. Swansea, /. R. 



Frond two to three times longer than broad, larger than that of Cosmarium 

 Cucurbita, which in form this species much resembles ; sides parallel, the 

 middle slightly constricted and the ends broadly rounded. Mr. Jenner finds 

 ver)^ faint, minute, scattered puncta after the escape of the endochrome. Mr. 

 Thwaites' s specimens were very gelatinous, but I was unable to ascertain 

 whether each plant had a distinct mucous covering, or was merely imbedded 

 in a common matrix. The transverse \'iew appears to me cyhndrical, but 

 Mr. Jenner finds the segments slightly compressed. 



Cosmarium Thwaitesii differs from C. Cucurbita in its larger size and in- 

 distinct puncta ; from C. curtum in its differently arranged endochrome ; and 

 from C. turgidum and C. attenuatum in its nearly parallel sides. 



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

 striction -g-L. 



Tab. XVII. fig. 8. a. fronds surrounded with gelatine ; b. empty frond ; 

 c. transverse view. 



31. C. curtum (Breb.) ; frond oblong, constricted at the middle and 

 rounded at the ends ; endochrome in longitudinal fillets. 



Closterium curtum, Brebisson, in Menegh. Synop. Destnid. in Linncea 1840, 



p. 237. Kutzing, Phycologia Germanica, p. 132. 

 Penium curtum, Brebisson, in lit. cum icone (1846). 



Near Bristol, Mr. Thwaites. Penzance, /. R. 



Falaise, Brebisson. Germany, Kutzing. 



