40 



by essential characteristics even in a sterile stage. Cp. the three 

 following species. 



Habitat. In the only certain locality hitherto known it forms 

 banks on a depth of 3 — 5 fathom, in a current in the inner part 

 of a fjord, in company with other species. Among numerous speci- 

 mens collected in the later half of September only a couple were 

 provided with reproductive organs in development, or parity sho- 

 wing scars after emptied conceptacles of sporangia and cystocarps. 



Occurrence. Found at Mestervik in Malangen (Tromso Amt), 

 local but abundant. A sterile and fragmentary specimen gathered 

 in the middle of June at Lyngo near Tromso probably belongs to 

 the same species. So also a couple of specimens found cast on 

 shore at Kragero on the south coast. 



Lithothamnion dimorphum Fosl. mscr. 



L. fronde libera in fundo jacente, sphserica vel subsphaerica, 

 roseo-purpurea, decomposito-subdichotome ramosa, ramis e centro 

 solido, exiguo, undique egredientibus, uno alterove ramulo brevis- 

 simo prgeditis, plus minus coalitis, teretibus vel subcompressis, 

 subaequalibus vel apicem versus parum incrassatis, vel interdum 

 attenuatis, 2 — 2.5 mm. crassis, fastigiatis, apicibus in parte thalli 

 inferiore plerumque obtusis vel truncatis vel interdum rotundatis, 

 in parte superiore plerumque truncatis vel interdum obtusis vel 

 demum disciformibus ; conceptaculis sporangiferis convexiusculis vel 

 ssepe plano-convexis, parum prominentibus, infra apices ramorum 

 creberrimis, a superficie visis diametro 400 — 450 fi; sporangiis 

 quaternas sporas foventibus, 100 — 140 /j. longis, 40—60 p. latis. 

 Tab. 10. 



Description of the species. The frond is in a younger stage 

 rather regularly spherical, but older occasionally getting somewhat 

 compressed, or forming subspherical or nearly hemispherical masses, 

 that attain a diameter of 10 cm., more commonly, however, about 

 8 cm. The colour is in winter, or the darker time of the year, 

 a dark pink with a purplish tinge, and nearly the same shade of 

 colour as deep-water specimens of L. tophiforme. In summer, on 

 he contrary, it gets much bleached, like most other Lithothamnia 



