No. 5] NEW OR CRITICAL CALCAREOUS ALG.E. 13 



f. agariciformis (Johnst.) Fosl. 



Calc. alg. Fuegia; Nullipora agariciformis Johnst. Brit. Sp. and Lith. p. 241, 



woodcut, no. 23. 



Melobesia agariciforniis Harv. Phyc. Brit. pl. 73. Non Aresch. in J. Ag. 



Spee. Alg. 2, p. 516. 



Lithothamnion agariciforrae f. hibernica Fosl. On some Lith. p. 5. 



Millepora agariciformis Pall. Elench. p. 263? 



f. lieterojjliylla Fosl. mscr. 



Lithothamnion agariciforme f. decussata Fosl. On some Lith. p. 5. 



I do not include Lithothamnion cmtarcticum (Harv.) here, as 

 I have not j^et had the opportunity to examine authentic specimens. 

 Cp. Fosl. Calc. Alg. Fuegia. 



The above f. pusilla partly much approaches L. antarcticum. 

 which as remarked 1. c. scarcely is any separate species, parti}- 

 showing transitions to f. patena. It also passes into f. depressa 

 and is not an^^ ^"ell defined form, but owing to its often pecLiliar 

 development ought to be speciall}" mentioned. As regards the 

 structure in this form contrar\' to that of f. patena cp. Rosan. 1. 

 c. pl. 5, fig. 3, 4 and 14. 



The form depressa is a characteristic form, recognisable by 

 its more or less plain and imbricate lamels, sometimes with the 

 edges bent a little downwards sometimes a little upwards, or now 

 slightly convex now slightly concave, and in the latter case b}- 

 and by passing into f. agariciformis. The semicircular or reniform 

 lamels, with entire, crenate or slightly lobed and often more or 

 less undulate margin, frequently are to be found in great number 

 over each other, at length forming crust-complexes up to about 

 1.5 cm. in thickness. Old specimens sometimes are nearly loosened 

 from the substratum which partly may be the rock itself partty at 

 first dense tufts of CoraUina, but then at length also spreading 

 over the rock. In the Irish specimens examined the imbricating 

 lamels are most commonly but here and there anastomosing, while 

 in specimens from the Atlantic as well as JMediterranean coast of 

 France the lamels sometimes are to be found coarser and more 

 anastomosing, or sometimes forming an almost solitarj', more or 

 less extended crust closety clinging to the substratum, thus in fact 

 even approaching Lithothamnimi Pliilippii in habit. 



