INVERTEBRATE BOTTOM FAUNA 513 



were : Spatangus purpureus, Echinocardium, Echinaster sangtiinolentus, 

 Liiidia sarsi, Hippasterias plana, Ophiopholis aculeata, Ophiothrix 

 fragilis, Scaphander, Hyas coarctatus, Pagiirus pubescens, Inachus 

 dorhynchus, Stenorhynchus longirostris, the annelids Thelepus circinnatus 

 and Leodice norvegica (both very common), etc. Some of these 

 are mainly littoral forms on our coasts. Inachus dorJiynchus and 

 Stenorhynchus longirostris seem to have a more westerly distribution than 

 the rest, the former being very rarely, and the latter never, found near 

 the Scandinavian coasts, though two , other species {Inachus dorsettensis 

 and Stenorhynchus rostratus) do occur there ; these four forms are 

 all met with on the North Sea coasts of Great Britain. From the deep 

 part of the plateaus we may mention the comparatively rare RJiizocrinus 

 lofotensis (see Fig. 356), which is fixed in the mud by root-like off-shoots. 



One locality examined by the "Michael Sars" in 1902 is Sheii-covered 

 entitled to special notice, viz. the extensive Faroe Bank to the ^^"^^* 

 south-west of the Faroes, v^here the bottom at a depth of 100 

 to 300 metres is peculiar, being quite covered with an enormous 

 quantity of empty shells of different mussels,^ with a few living 

 specimens among them.- The empty shells were pure white, 

 and it was interesting to see how this white colour affected the 

 other bottom-animals, fishes as well as invertebrates. A couple 

 of species of Raia, for instance, had large white spots, and a 

 flounder i^Plezironectes Imianda) had assumed the light colour of 

 the bottom ; Ophiiira albida, which on our coasts and elsewhere 

 is of a blackish-brown colour, was here perfectly white, and the 

 spines of Echi7ius esculentus were far lighter in colour than 

 usual. Astacilla longicornis, which climbed about among the 

 hydroids, had on the other hand assumed their green hue. 



The geological significance of these shell-covered banks 

 (there are several round the Faroe islands, and fossil shells are 

 also found on the Norwegian coast-banks) has been discussed at 

 considerable length by Professor Brogger.^ They are generally 

 believed, like the Norwegian coast-banks and the plateaus 

 round the Shetlands, etc., to have stood at a higher level during 

 the glacial and inter-glacial periods, forming part of the littoral 

 region of the sea-floor, and to have since subsided. The fossil 

 remains of animals that along our coasts nowadays appear to be 

 able to live, or at any rate to thrive, only in shallower waters 

 are taken as proof of subsidence, it being assumed that with the 

 subsidence of the bottom this shallow-water fauna became 

 extinct. 



1 Pecticnculus glycimeris, Venus casina, Tellina crassa. Area tetragona. Tapes eduHs. 



2 Pedunculus glycimeris, Venus casina, Tellina crassa, Mactra elliptica, Psatit7Hobia iellinella, 

 and Dosinia. 



^ " Oni de senglaciale og postglaciale nivaaforandringer i Kristianiafeltet (Molluskfaunaen)," 

 Norges geoL Undersogelse, No. 31, pp. 106, etc., Kristiania, 1900-1901. 



2 L 



