Mr. Jeffreys informs me that, in addition to the above, there are many other species in the same category, though they have not yet been specially recorded. According to him, the total number of species which were, until lately, considered extinct, but which he has now ascertained to be living, is at least thirty.
In the Mediterranean, there is at present little to record. 15 species were dredged from a depth of 8490 feet. They consisted of:—
Northern species. 5
Lusitanian 9
Oceanic 1
Fossil in Italy 9
Fossil in the Crag 4
New species 2
Some new species of much interest were discovered in less depths (of from 100 to 1000 feet) in and at the entrance of the Mediterranean. Amongst these there were 31 northern species, also 12 species before known only as fossil in Italy, and 3 species common to our Crag.
Thus, so far from showing any relationship to the Cretaceous fauna, the deep Atlantic mollusca have their nearest allies in Pliocene (and possibly Upper Miocene) forms of Italy and in those of the Crag-beds of this country. Mr. Jeffreys's anticipations, made in 1862 *, that " it is highly probable that all the mollusca which lived during the periods represented by the newer strata still survive in some part or other of those vast tracts of sea-bed which lie between the North Pole and the Pillars of Hercules," and that the deeper recesses of the ocean would be found inhabited, receive therefore great confirmation, though it yet remains to be seen to what extent they may be fully realized. Almost all the species yet found at these great depths are, like so many of our Coralline-crag species, very small.
Prof. Duncan has described† 12 species of corals dredged from depths of from 2000 to 4200 feet ; and he informs me that he has under description many others, some of which were obtained from a depth of 6570 feet. Owing to the great range in depth and temperature of the Atlantic sea-bed, the variation in form of some of the corals has been so excessive that Prof. Duncan has absorbed 9 old species in the 12 now established. The range and distribution of these species thus obtained in the first and second expeditions is very remarkable.
- ' British Conchology,' Jeffreys, vol. i. p. xci.
† Proc. Roy. Soc. vol. xviii. p. 289.
