TRANSACTIONS OF SKCTION D. 



751 



,d the Pliormii- 



each bottle containin;? a specimen the depth from which the net in wliich the 

 specimen was found had been dravrn np. In many instances, from the nature of 

 the ppecimen, it is impossible that it can have come from anywhere but the 

 bottom, but in manj' others it is quite possible that a particular specimen may have 

 entered the net at any intermediate depth, or close to the 'urface, and this is a 

 matter on which the author of the monograph in which tlie sp.;cimen is described 

 can form the best conclusion, if one can be formed at all from his knowledge of 

 the animal itself. In all doubtful cases the mere record of the depth must be 

 received with caution. 



Just as before the commencement of the present period of deep-sea research 

 there was a strong tendency amongst naturalists, owing to the influence of the 

 viev3 of Edward Forbes, to refuse to accept the clearest evidences of the existence 

 iif starfish and other animal life on the sea-bottom at great depths, so there seems 

 now to have sprung up in certain quarters an opposite tendency, leading to the 

 assignment of animals possibly of surface origin to great depths on inconclusive 

 evidence. 



With regard to tlie constitution of the deep-sea fauna, one of its most 

 remarkable features is the general absence from it of Palaeozoic forms, excepting 



far as representatives of the Mollusca and IJracliiopoda are concerned, ,and it ia 

 reraarkuble that amongst the deep-sea mollusca no rejjresentatives of 1 lie Naiitildce 

 and Ammonitida, so excessively abundant in ancient periods, occur, and that Li/if/ula, 

 the most ancient Iiracliio])od, should occur in shallow water only. 



Tliere are no representatives of the most characteristic of the Paheozoic corals, 

 sucii as Zaphrentifi, Cijstiphylhuu, Stauria or Goniop/ii/Uum. Possible representa- 

 tives of the C;/nf/io/i(i.n'dfe liave indeed been obtained in Guynia, described by 

 Professor Martin Duncan, and HaplophtjlUa and Dunaaiu/, described by the 

 late Count Pourtales, but the Cjj(itho)ia.v{d(e are the least aberrant and characteristic 

 members of so-called litu/osfi. Pourtales justly felt doubtful wiiether the arrange- 

 ment of the septa in four systems instead of six could in itself be considered as a 

 criterion of the Rvyosa,'^ and in the cases of Ilaplophjillia and Duncania the 

 septa may be described rather as devoid of any definite numerical arrangement 

 than exliibiting any tetrameral grouping. Further, I have lately examined by 

 means of sections the structiu'e of the soft parts of Duncania in a specimen 

 kindly given to me by Mr, Alexander Agassiz for tlie purpose, and find that with 

 regard to the peculiar arrangi ment of the longitudinal septal muscles and the 

 demarcation of the directive septa the coral agrees essentially with the Hexactiuian 

 Can/op/ii/llia and all other modern Madreporaria the anatomy of whicli has been 

 adequately investigated. 



There are further no representatives of the ancient Alci/onarianfi, forming 

 massive coralla, the Hcltopor'uhe and their allies, in deep water, no raUeocrinoidx, 

 Cyntidea, or Blastoidea, no I'nlechinoidea , no Trilohites, no allies of Limulus, no 

 Gmwid-i. Further, otlier ancestral forms, certaiiUy of great antiquity, although 

 unrecorded geologically, such as Amphio.vui^, do not occur in deep water. It might 

 well Iiave been expected that, lad the deep sea been fully colonised in the Palaeozoic 

 period, a considerable series of representative forms of that age might have 

 Mirvivid there in the absence of most of the active physical agents of modification 

 ".vhieli characterise the coast regions. 



From the results of ]nesent deep-sea research it appears that almost all modei'n 

 littcH'al forms are capable of adapting themselves to the conditions of deep-sea 

 life, and there is no reason wliy Paheozoic form hould not have done so if the 

 abyssal conditions were similar to those now existing, just as a considerable number 

 of forms of the chalk period have survived tiiere. In fact, however, most of 

 survivals of very ancient forms — Ilcliojyora, Limulu,<>, AmpJdoxvi^, Ui'jmoi, Ganoids — 

 occur in shallow seas or fresli water. 



With regard to the origin of the deep-sea fauna, there can be little doubt that 

 it has been derived almost entirely from the littoral fauna, which also must have 



' ' Zoological Results of the Ilasslcr Expedition.' 

 rurd, No. viii. 1874, p. 41. 



See Cat ^fus, Conq). Zool. Ilar- 



il!: 



