71 



b. Vertical distribution. 



The specimens which I have examined of the present species of Brisinga were all 

 taken from about the same depth, namely 250 300 fathoms. Nevertheless it goes, as has 

 been proved, considerably further down into the deep. In the Fseroe channel it was taken 

 form a depth of 500 fathoms ; and off the west coast of Ireland it was found at the depth 

 of even 800 fathoms. In all probability 200 fathoms must be considered as its highest 

 limit. Whether it goes even lower than 800 fathoms, is not yet certainly decided; but yet 

 it seems to me very probable that it goes at least as deep as the other species Br. ende- 

 cacnemos, which off the Portuguese coast has been taken in 1000 fathoms. The highest limit 

 for this last species seems to be about the same as for Br. coronata, namely about 200 

 fathoms. 



c. External conditions of existence. 

 Special occurrence. 



All my specimens of Brisinga coronata were taken at a considerable distance from 

 the shelving bank of the coast, on an even and flat bottom covered with a more or less 

 thick layer of clay or mud. It appears to have been taken under the same conditions 

 during the atlantic expeditions; but the occurrence of the other species seems to be very 

 dissimilar. It has been always found by Asbj0rnsen, as well as by myself, only nearer to 

 the coast on the steep bank which rises from the deeps "outside, where the bottom is rocky 

 or stony without any deposit of mud or sand. Whether this dissimilarity in occurrence 

 between the two species is the same everywhere, I do not venture to say; as this is not 

 sufficiently clear from the reports of the atlantic expeditions which we possess. But on our 

 coast the conditions appear to be perfectly constant. The temperature in which the Br. coro- 

 nata lives at Lofoten is, according to the investigations made by me in the summer of 1869, 

 about -f- 4 C.; but it is necessary to remark that I had at the time only a very imperfect 

 deep-sea thermometer at my disposal. It is thus very possible that the temperature may 

 have been in reality somewhat lower, which would also agree with the statement of tempera- 

 ture communicated in the report on the Lightning's" expedition. It occurred, according to this 

 report, only in the cold area in the Faeroe channel, where the temperature, at the depth of 500 

 fathoms, was only a little above the freezing point.. Off the west coast of Ireland it seems 

 however to have been taken by Jeffreys in a much higher bottom-temperature. It appears never- 

 theless from other circumstances of the animal's occurrence here, that the Fauna exhibited on 

 the whole a decidedly northern character. In Lofoten it was found together with Astropecten 

 Andromeda and tenuispinus, Echinus norvegicus, Stichopus natans, an enormous number of 

 Ulocyathus arcticus. various Molluscs, among which Admete viridula, Trophon barvicensis, 



