MONORMIA. 285 



1. Trichormus incurvus Alhn. 



Plate LXXV. Fig. 1.? 



Char. " Plant cither diffused through the icater or collected on 

 the surface. Filaments of a pea-green colour, crowded 

 together confusedly in a gelatinous matrix, variously curved, 

 but never regularly spiral, assuming, lohen dried, a fine 

 verdigris-green colour without lustre.^'' — Allman. 



Allman in Annals of Nat. Hist. vol. xi. p. 163. 



Hab. In the Grand Canal dock, Dublin, October : Dr. 

 Allman. 



The only authentic specimen which I have seen of this 

 species was so much injured that I was not able to make an 

 examination of it in the least satisfactory. A specimen, how- 

 ever, sent me by Mr. Thompson, collected by that gentleman 

 and found floating on the surface of Lough Neagh, at Shane's 

 Castle, marked Anabaina Jlos-aquce, accords so well with the 

 description and figure given by Dr. Allman of T. incurvus, 

 that scarcely a doubt remains as to the propriety of regarding 

 Mr. Thompson's plant as that species, see PI. LXXV. fig. 1. 

 From the true A. flos-aquce Mr. Thompson's specimens differ 

 in the less considerable dimensions of the filaments, and in 

 the absence of the enlarged cells. 



Section ii. 

 Filaments invested in a mucous matrix of a definite for 7n. 



37. MONORMIA Berkeley. 



Char. " Frond branched, composed of a single moniliform 

 thread, following the ramifications, immersed in gela- 

 tine.'''' — Berk. 



Derivation. From fxcvos, one, and opfios, a necklace. 



This genus scarcely diflers from Nostoc, between which and 

 Anabaina it forms a clear link. 



