238 JORDAN : ON THE GENUS FUSUti 



17. — Fusus sarsi, Jeffreys. 



'Knight Errant' expedition, station 5, 515 fathoms, bottom 

 temperature 45 "4^ Fahr. 



Of this species also I have been unable to find any figure 

 or description. 



18. — Fusus lachesis, Morch. 



'Knight Errant' expedition, station 2, 375 fathoms, bottom 

 temperature 31 'o^ Fahr,; station 8, 540 fathoms, bottom tem- 

 perature 29*2^ Fahr. ; on the ridge, sounding No. 7, 300 

 fathoms, bottom temperature 48-0" Fahr. 



The above affords another illustration of the competency 

 of moUusca to accommodate themselves to a considerable range 

 of temperature. In this case the range is nearly 19-0'' Fahr. in 

 comparatively a few miles. 



CONCLUDING REMARKS. 



The occurrence of Fusus Islatidicus and F. fenestratus off 

 the south-west of Ireland is a very interesting fact, and the 

 question arises : — " Are these Arctic species a survival from the 

 'glacial epoch,' or have they migrated south subsequently?" 

 This question really forms part of a larger one, for the following 

 Arctic species occur in similar, and even in lower, latitudes : — 

 Fusus despectus, Leda frigida (this species lives also at Spitz- 

 bergen and Finmark), Verticordia abyssicola (Finmark), were 

 dredged off Valentia ; Terebratula Spitzbergensis, 185 miles 

 off Cape Clear ; Terebratula cranuwi, Fusus fenestratus, Leda 

 abyssicola, Siphonodentaliu7n vitreu?/i, Sic. (all Arctic species), 

 were dredged off the coast of Portugal, near the mouth of the 

 Tagus, 600 — 1,095 fathoms, the lowest bottom temperature 

 being 39"7'' Fahr. 



The reason usually assigned for the disappearance — at all 

 events in part — of Arctic forms of life, which we know by their 

 fossil remains lived in the British area during the glacial epoch, 

 is that the higher temperature which set in was inimical and 



J.C, vi., July, 1890. 



