4 M. FOSLIE. TWO NEW LITHOTHAMNIA. [1903 No. 2] 



Lith thamnion lamell a tum Setch. et Fosl. mscr. 



Thallus lamellate, scantil^^ prolificating, horizontally extended 

 and partl}^ attached ; conceptacles of.sporangia subprominent, flattened 

 in the central parts, 350—600 ji in diameter. 



This species forms suborbicular or irregular lamels, which in 

 the specimens seen are scantilj^ prolificating, 2 — 3 cm. in diameter 

 and 300—500 jj- thick. It seems to have been loosely attached 

 to rocks or stones and at the same time covering or in part attached 

 to other Algae, especially Corallina, but on the other hand rather 

 clinging to the substratum, with more or less free margin, somewhat 

 lobed and undulate. In the lower part of the plant small scutellate 

 or cupulate new thalli occasionally are formed, which little by little 

 become confluent, partly resembling similar formations in LitJio- 

 X>hyUum expansum. 



A vertical section of an almost freely developed part of a 

 crust shows a vigorous hypothallium composed of cells which are 

 frequently 18 — 32 /^ long and 5 — 8 jj- thick, sending forth rather 

 short perithallic rows partly upwards, partly here and there even 

 downwards too. The perithallic cells are much varying in length, 

 partly almost square, partly and most frequently vertically elon- 

 gated, 8 — 15 //-, now and then 18 jj. or occasionally even up to 

 24 IX long. 



The conceptacles of sporangia are developed almost every- 

 where except in the peripherical portions of the thallus and are 

 as a rule crowded. They are subprominent, at length flattened 

 or now and then slightly depressed in the central parts, 350 — 600 /x 

 in diameter when seen from above, traversed by 40 - 60 coarse 

 muciferous canals. The sporangia are four-parted, about 250 // 

 long and 120 fi broad. 



The species stands near to L. syntrophicum and in structure 

 it also approaches L. conchatum. On the other hand it reminds 

 one much of certain forms of L. lichenoides. 



It is only known from California, where it has been collected 

 •at Dypress Point, Aionterey County by W. A. Setchell and 

 R. E. Gibbs. 



