140 



HYDROIDA II 



Iceland: Danmark Strait 66°2o' N., 25°i2' W., depth 96 fathoms 

 Adalvik, depth 5,5 fathoms (on roots of Laminaria). 



The Faroe Islands: 6 miles N. by W. of Store Kalso, depth 60 fathoms 

 Vestmanhavn (depth not stated) 



Deep hole of north point of Nolso, depth 100 fathoms 

 16 miles E. by S. of south point of Nolso, depth 80 fathoms 

 Boronses 13 miles N. 75 W., depth 30 fathoms. 



Quite young colonies of Thujaria thuja are pinnate, and very difficult to distinguish from small 

 colonies of Thujaria laxa Allman. The broad plane of the branches in such specimens, up to a couple 



Fig. LXXV. The distribution of Thujaria thuja in the Northern Atlantic. 

 In the hatched regions a common occurrence is recorded. 



of centimetres high, is vertical, and the branches are single. Here, however, the hydrotheca at the 

 tip of the branch, which is of the Sertularia type, will as a rule reveal the identity of the species. 

 The occurrence of this type of hydrotheca in Thujaria thuja is, as I have previously pointed out (1905) 

 of considerable interest, as giving us a hint of the derivation of the Thujaria species from Sertularia. 

 Thujaria thuja is a boreal species, capable of moving far to the south; it is said to have been 

 found both off the coast of Portugal and in the Mediterranean, but is not common south of Ireland. 

 On the other hand, it does not enter the purely arctic waters; it has its chief distribution in the deep 

 littoral region, but may occasionally be met with in the abyssal, and even deep down in the same, 

 as is seen from the finds of the "Ingolf" at St. 95 and 96. In the North Atlantic (fig. LXXV) the 



