, 



No. 3] REMARKS ON NORTHERN LITHOTHAMNIA. 131 



Addenda and Corrigenda. 



Lithothamnion lave (Stromf.) Fosl. — Cfr. pag. 16. 



After having a part of this paper printed, Dr. Rosenvinge 

 kindly sent me some more Lithothamnia for examination. Among 

 these is a specimen from Denmark probably belonging to the above 

 species It has been collected S. E. of Hesselo in the Cattegat in 

 a depth of 15 fathoms (Rosenvinge!). The crust is about 2,5 

 by 2 cm. in diameter, covering a small fragment of a mollusk 

 (Mya?) and a tube of a Serpula attached to the said mollusk. It 

 is about 100 >)- thick and bears a few conceptacles of sporangia. 

 The latter are 500 — 650 /j- in diameter and coincide with those in 

 the said species. The specimen was collected the 17th of Jury, 

 and in a single conceptacle examined I found three sporangia un- 

 parted, one two-parted, and one apparently three-parted. It was 

 found together with an entire mollusk (Cyprina) and a fragment 

 of another one bearing some quite young crusts of a similar cal- 

 careous alga, and besides a pebble to which is attached a small 

 crust resembling the latter as well as two young ones of Lithoth. 

 Granii. There could perhaps be a possibility that the specimen 

 in question and the first named young crusts also represent 

 a young form of the latter species. However, it does not show 

 any trace of branches founded, and the conceptacles are differing 

 in shape and larger than in L. Granii. Nor have I seen concep- 

 tacles developed in the crust of this species. On the other hand, 

 the alga approaches in habit certain forms of Lithoth. Sonderi, 

 but the conceptacles are too large and too prominent, and besides 



