448 Mr. J. Gwyn Jeffreys oti Dr edging-Reports. 



LX. — Reports on Dredging. By J. GwYN Jeffreys, F.R.S. 



I HAVE not much to say in answer to the remarks made by 

 Mr. M^ Andrew in the last Number of the ^ Annals/ because 

 it seems to me that we do not differ in any very material 

 point. 



With regard to " bathymetrical " zones (in which, of course, 

 I did not mean to include that part of the shore which lies 

 "beyond the reach of ordinary tides"), I am satisfied with 

 my friend's admission that " the same species often frequent 

 different depths in different seas :" from my own experience in 

 dredging (now of between thirty and forty years) , I would say 

 the same seas. I am not a disbeliever in zones, having, in my 

 work on ^ British Conchology,' adopted and endeavoured to 

 define four, — viz. littoral, laminarian, coralline, and deep- 

 sea ; but the first two and last two of these constitute two 

 principal zones, which may be termed littoral and submarine. 

 Some species of Mollusca, as well as of other animals, range 

 from low-water mark to the greatest depth reached by the 

 dredge. 



The question as to the comparative size of northern and 

 southern specimens of the same species was so fully discussed 

 by us in the ^ Annals ' for 1860, that it is unnecessary to con- 

 tinue the controversy. I would, however, observe that perhaps 

 our disagreement on this point may in some measure arise 

 from my considering certain forms mere varieties which other 

 conchologists hold to be distinct species. I have elsewhere 

 given my reasons for uniting Pecten septemradiatus with P. 

 clavatus^ Lima Mans with L. tenera^ and Astarte sulcata with 

 A. elliptica and A.fusca or incrassata. The last named in 

 each case I regard as the southern form, and the others as the 

 northern form of those three species. Mr. M'Andrew did not 

 find Pecten septemradiatus on the Scandinavian coast so large 

 as those of Loch Fyne. A valve from the Faroe banks, 

 dredged by Dr. Carpenter and Professor Wyville Thomson, 

 measures an inch and nine-tenths in length ; this far exceeds 

 any I have seen from Loch Fyne, where the species is com- 

 mon. He also says that his specimens of Astarte sulcata from 

 Gibraltar and from Finmark are equal in size ; and he agrees 

 with me that size diminishes with depth. His dredging-lists 

 record that species from 45 fathoms at Gibraltar and 15-160 

 fathoms on the western coast of Norway. Possibly his Fin- 

 mark specimens came from the deepest water, and were con- 

 sequently smaller than those from Gibraltar. But even if it 

 were not so, my proposition was qualified; and every rule has 

 its exception. 



