-18 BRITISH D£SMIDI£^. 



Tab. XXXV. fig. 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. 



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



p. 127. f. 3. 

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



United States, Bailey. 



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

 formed by whorls of tubercles. 



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

 corresponding 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 drawings 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. 



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

 Worden's Pond, Rhode Island, Bailey. 



" This species is at once distinguished from Bocidium 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. 2). 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, 1846, 

 V. l.p. 127. i. A. 



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, I. c. 



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

 tooth-like projections ; ends with three bidentate processes. 



Bocidium verticillatum, Bailey, in lit. cum icone (1847). 

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



\A'orden's Pond, Rhode Island ; Princeton, New Jersey, Bailey. 



