218 BRITISH DESMIDIE^. 



Tab. XXXV. tig. 6. a. empty segment ; b. end view : from drawings by 

 M. de Brebisson. 



9. D. nodosum (Bailey) ; frond stout ; segments with four prominent 

 nodes separated by constrictions ; end view crenate. 



Clusteriwn nodosum, Bailey, Amer. Journ. of Science and Arts, 1846, v. 1. 



p. 1 27. f. 3. 

 Docidmm nodosum, Bailey, in lit. cum icone (1847). 



United States, Bailer/. 



An end view shows that each node is not a simple swelling, but really 

 formed by whorls of tubercles. 



" This species is easily recognised by the deep indentations in its outline, 

 corresponduig to the constrictions which separate the transverse rows of knot- 

 like projections. It is one of the largest species in the genus." — Bailey, I. c. 



Tab. XXXV. fig. 8. a. empty segment ; b. end view : from dravdngs by 

 Professor Bailey. 



10. D. constrictum (Bailey) ; frond stout; segments with moderately 

 deep constrictions, which separate four equal, gently curving pro- 

 minences ; end view entire. 



JDocidium constrictum, Bailey, in lit. cum icone (1847). 

 Worden's Pond, Rhode Island, Bailey. 



" This species is at once distinguished from Docidium nodosum by the cross 

 section of the nodes being a simple circle instead of an indented one." — 

 Bailey, in lit. 



Tab. XXXV. fig. 7. from drawings by Professor Bailey : a. front view ; 

 b. end view. 



11. D. verrucosum (Bailey) ; segments with numerous whorls of 

 small prominences which give the margins an undulated appear- 

 ance, all the undulations equal. 



Closterium verrucosum, Bailey, American Journal of Science and Arts, 1 846, 

 V. 1. p. 127. f. 4. 



New York ; Rhode Island, Bailey. 



" This is a very pretty species with a waved outline, caused by the slight 

 projections, which are arranged in numerous transverse rings." — Bailey, /. c. 



12. D. verticillatum (Bailey) ; segments with numerous whorls of 

 tooth-like projections ; ends with three bidentate processes. 



Docidium vei'ticillatum, Bailey, in lit. cum icone (1847). 

 Triploceras verticillatum, Bailey, in lit. (1847). 



Worden's Pond, Rhode Island ; Princeton, New Jersey, Bailey. 



