139 



specimen of the latter, but according to Kjellman 1. c. the con- 

 ceptacles appear to be of about the same size in both, in the 

 named species „markbara pa krustans yta genom en deras tak 

 omgifvande, svagt upphojd kant", but I do not know whether this 

 border is formed in the same manner as in the present species, in 

 which it has not been raised above the original surface of the 

 frond. The structure appears to be somewhat differing, and the 

 sporangia are tetrasporic in L. durum, but in L. evanescens they 

 most probably are bisporic. 



Sterile and especially younger specimens appear to be easify 

 confounded with L. coalescens or L. circumscriptum. 



Habitat. The named specimen found with us was fastened 

 to a Mytilus shell together with L. colliculosum and L. Stromfeltii 

 on a depth of 5 — 6 fathom in the inner part of a fjord. It is 

 gathered in the later half of September and has been rather richly 

 provided with conceptacles of sporangia, nearly all of them, ho- 

 wever, emptied, and the scars partly effaced. On the American 

 •coast the plant has been taken „just below low water mark", 

 nearly encompassing a small stone, in April partly richly provided 

 with sporangia partly with emptied conceptacles. 



Occurrence. Found at Mestervik in Malangen, not far from 

 Tromso, a solitary specimen. 



Geogr. Distribution. The Atlantic coast of North America 

 (Collins). 



Lithothamnion laevigatum Fosl. mscr. 



L. fronde Crustacea, subarcte adnata, 0.3—0.8 mm. crassa, 

 lsevissima, subnitida, violaceo-purpurea, livida vel flavescente; con- 

 ceptaculis sporangiferis sub foveola demum fere hemisphaerico- 

 concava annulo vix elevato circumdata immersis, diametro 150 — 

 .200 fi; sporangiis binas sporas foventibus, 120 — 150 /J. longis, 

 40-60 fi latis. Tab. 19, fig. 21—23. 



Syn. Lithothamnion crustaceum Batt. herb. 



Remark on the species. I have seen but a couple of fully 

 developed Norwegian specimens and some other young ones pro- 

 bably belonging to the same species, but several from abroad. It 



