No. 3] REMARKS ON NORTHERN LITHOTHAMNIA. 69 



scribed by Ellis et Solander, Zooph. p. 129, t. 23, fig. 13 and 

 quoted by Areschoug 1. c, seems to me more likely to repre- 

 sent a coral, whereas the Millepora polymorpha Ell. et Sol. de- 

 scribed 1. c. p. 130 is an unquestionable L. calcareum. 



In Lithoth. Adriat. Meer. etc. p. 11 and p. 33 I suggested that 

 L. coralloides seems in fact only to be a form of L. calcareum. 

 After succeeding in finding conceptacles in specimens of both which 

 I presumed to be typical ones, I must now subsume the former 

 under the latter. 



As to the forms of the species is to be observed that f. 

 squarrulosa is the bigger form and mostly the coarser one. It 

 includes f. valida, which I do not now admit as an independent 

 form, because it in the main only represents a coarse or partly 

 monstrous variety of the said f. squarrulosa. The form coralloides 

 is smaller, often with branches comparatively shorter, but other- 

 wise no real line can be drawn between them. It runs into f. com- 

 pressa. The latter form is flabellate, the branch-systems spreading 

 like a fan in all directions from the centre of the frond almost in 

 one plane. Sometimes it forms rather thick and compressed fronds. 

 A form nearly approaching and faintly differentiated is f. palma- 

 tifida, with branches more distant and palmate, but otherwise re- 

 sembling the former. Cp. Lithoth. adriat. Meer. etc. t. 2, fig. 22. 

 I admit it as an independent form, because it seems to proceed 

 from f. squarrulosa, while f. compressa has risen from f. coral- 

 loides. Cp. Lithoth. Adriat. Meer. etc. t. II, fig. 22, which repre- 

 sents a form intermediate between typical f. palmatifida and f. 

 compressa. The form subsimplex is but a simple or feebly branching 

 f. squarrulosa. The f. minuta, admitted 1. c , on the contrary, 

 has proved not to belong to the species in question, but to be a 

 delicate form of Lithoth. fruticulosum, and is perhaps identical 

 with f. soluta described in Lithoth. Adriat. Meer. etc. p. 7. Cp. 

 1. c. t. 1, fig. 18—33. 



The conceptacles of sporangia in this species are partly scat- 

 tered, partly somewhat crowded, 250 — 400 ;j- in diameter, immersed 

 or subimmersed, at first convex, but by and by decorticated in 

 the central part of the roof, where at last they become concave or 



