AXTITIIAMNTOXELLA, A XKW GENUS OF M.iLV. 



317 



Two rather small algse, winch resemble the new plant very closely, 

 both in structure, verticillate nature of small branches, and character 

 of the tetrasporanges — Antithamuion ternifolmm and A. verticii- 

 latum, both from the Southern Hemisphere, doubtfully referred by 

 De Toni to Antithamiiloii, probably on account of the two kinds of 

 branching. These and the plant from Guernsey possess a combina- 

 tion of characteristics which, though agreeing in one or more points 

 with Callitliamiiion, ^permotliamnion^ and Antithamnion, do not 

 conform completely to any of the three. I propose therefore to 

 unite these plants under a new genus, Antlthamnionella, on account 

 of the verticillate arrangement of the smaller branches round a 

 central axis ; only those algse with verticils of simple ramelli have 

 been included. Of this the following is a description : — 



Frons caespitosa, tilamentosa, articulato-monosiphonia, alterne 



Fig. 1. — Antithamnionella sarniensis Lyle. X 2. 



verticillatimve et fasciculatim ramosa, ramis iterum repetite divisis et 

 sub-divisis. Cystocarpia bilobis. 



Plants monosiphonous and filamentous, with irregular alternate 

 and indefinite ramification. Whorls of 2 to 4 ramelli at each joint 

 crowded towards the extremities. In the whorls of the older portions, 

 one or more ramelli are occasionally replaced by discoid rhizoids. 

 Tetrasporanges solitary, ovoid, sessile on inner angles of ramelli, 

 triangularly divided. Cvstocarps bilobed. 



2a 2 



