BATHYMETRICAL DISTRIBUTION. 



■ Only slight materials are at present available for drawing any conclusions as to the 

 Bathymetrical Distribution of the Cephalopoda. This is due, in the first place, to the 

 fact that it is only quite recently that any record has been kept of the depth from which 

 specimens were obtained, all our museums having considered it sufficient to indicate 

 the localities of the various species. 



Since the introduction of deep-sea dredging, however, a change in this respect has 

 set in, but even yet the collections of the Challenger and of the United States Fish 

 Commission and Coast Survey furnish by far the greater proportion of the accurate data 

 available for discussion, although, no doubt, the investigations of the " Talisman " and 

 " Travailleur " will furnish welcome additions when published. 



Another consideration, however, greatly diminishes our real knowledge in this 

 matter, and it is the fact, which has often been commented on in the present series of 

 Reports, that it by no means follows that specimens procured necessarily inhabit the 

 greatest depth reached by the dredge. In the case of animals so gifted with locomotor 

 powers as the Cephalopoda it is peculia,rly impossible to obtain certainty in this respect, 

 and, consequently, every recorded instance of the occurrence of a member of this group 

 in deep water requires to be discussed on its own merits, and by the aid of whatever 

 collateral evidence may be available. 



Before proceeding further it will be well to give, in a tabulated form, the information 

 yielded by the Challenger collection, supplemented by whatever could be obtained from 

 the literature of the subject or other trustworthy sources. No general statements, such as 

 " shallow water," " moderate depths," have been admitted, but only those in which a 

 definite number of fathoms was recorded ; had the former been included the list of 

 species found above the 100 fathom line would have been much more extensive. 



The figures indicate the depth in fathoms, and the letters the sources of information ; 

 thus : — 



Ch = Challenger collection. 

 K = "Knight Errant" collection. 

 P = " Porcupine " collection (Expedition of 

 1869). 

 The numbers enclosed in square brackets indicate recorded depths which are almost certainly erroneous. 



(ZOOL. CHALL. EXP. PART XLVI. — 1886.) Xx 29 



S = Professor G. 0. Sars. 

 T = " Triton " collection. 

 V = Professor Verrill. 

 Val = "Valorous " collection. 



