No. 5] NEW OR CRITICAL CALCAREOUS ALG.E. 9 



crust it sends forth a bundle of simple or irregularly and scantily 

 divided, Short and rather anastomosing branches up to a height 

 of about 1 cm. The branches are about 2 mm. thick with rounded 

 tips. Also the lower parts of the crust occasionally issue short 

 and simple branches. 



The conceptacles of sporangia are rather crowded especially 

 in the upper part of the branches, subprominent, 400 — 500 p. in 

 diameter, at first convex but aftervvards depressed in the central 

 parts and here intersected with about 25 ralher delicate muciferous- 

 canals. The latter are not visible till the roof becomes depressed, 

 and this depression appears perhaps to be due to a decortication 

 of the named parts. I have not seen the sporangia, as several 

 conceptacles examined have been attacked by inferior animals, and 

 the sporangia destroyed but not the conceptacle itself. 



A longitudinal section of a branch shows regular cup-shaped 

 layers of tissue, the upper cells of which are rectangular, often 

 with rounded corners, 12 — 20 p long and 7 — 10 p broad. 



The plant appears to be most nearly related to Lithothamnion 

 Bornetii, the conceptacles much resembling those in the latter, 

 only larger, but also differing by the crust sending forth short 

 branches, as well as with reference to the structure. 



It has been tåken at the Cape of Good Hope, but the locality 

 is unknown to me, kindly communicated by Dr. H. Becker. 



Lithothamnion erubescens Fosl. mscr. 



Syn. Lithothamnion mamillare Dickie.l) 



Thallus forming on corals or rocks up to 0.7 mm. thick crusts 

 from which issue subdichotomous, crowded bi-anchsystems, with 

 terete or subcompressed, 1.25 — 1.75 mm. thick, short, fastigiate 



Dicl\ie, Enumeration of Algæ Irom Fernando-Noronha. Linn. Soc. Journ. 

 Bot. Vol. XIV. Pag. 363. 



Report on the Botany of the Bermudas and various other Islands of the 

 Atlantic and Southern Ocean ; Fernando-Noronha and Contiguous Islets. 

 Rep. Challenger Exp. I. Sec. Part. Pag. 27. 



The specimens under the above name determined by Dickie include 

 more than one species, but not identic with G. mamillare (Harv.), according 

 to authentic specimens of the latter that I have seen. 



