No. 5] NEW OR CRITICAL CALCAREOUS ALGÆ. l7 



Lithothamnion Aluelleri Lenorm. 

 in herb. ; Rosan. Melob. p. 101. 



f. cingens Fosl. 



Calc. alg. Fuegia. 

 Lithothamnion Muelieri Rosan. 1. c. t. 6, fig. 8. 



f. neglecta Fosl. 



Calc. alg. Fuegia. 

 Lithothamnion iichenoides Dickie in Journ. Linn. Soc. Vol. XV. Pag. 200, and 

 Phil. Trans. Ro}'al Soc. London. Vol. 168, Pag. 58. 



This spedes is like most other Lithothamnia much varying. 

 The form described by Ro sa no ff 1. c. accords with the original 

 type, but is perhaps not to be considered the typical form itself 

 of the species. I have named it f. cingens, because it frequently 

 surrounds partly the stem partly also other parts of other and 

 especially rather coarse cylindrical algæ. So it also covers the 

 root of divers algæ and then forming transitions to f. neglecta. 

 Such an intermediate form is probably that described by Heydrich 

 in Ber. d. deutsch. bot. Ges. Bd. 15, Pag. 51 under the name of 

 Lithophyllum rlvizomae, with conceptacles of cystocarps, which in 

 the present species generally are to be found in other individuals 

 than those of sporangia. 



In specimens of f. cingens surrounding other cylindrical algæ 

 the crust sometimes send forth in a right angle lamels which grow 

 free in a rather considerable extent, to a certain degree resembling 

 the below mentioned formations in Lithophyllum incrustans and 

 other species. 



The form neglecta is characterized by its rather extended and 

 more or less imbricate thallus, often with smaller or larger lamels 

 which are more or less confluent, at length forming rather thick 

 crust-complexes. 



The present plant represents an intermediate species in a link 

 of a group of the genus Lithothamnion, the species of which are 

 mutually nearly connected, and apparently almost running into 

 each other, as L. Iichenoides, L. Engelhartii, L. capense, L. 

 Jcerguelenum and L. Philippii. It is, however, on the one side 

 most nearly related to L. Iichenoides and on the other to L. 



