486 RECENT BRACHIOPODA chap. 



The vertical range of depth of certain species is great ; Tere- 

 hratala vitrea is recorded from 5 to 1456 fathoms, T. Wyvillei 

 from 1035 to 2900 fathoms. This is to some extent explic- 

 able since, after a certain depth has been reached, many of 

 the external conditions, such as absence of temperatm^e and 

 light, must remain constant even to the greatest depths of the 

 ocean. 



The area of the ocean explored by dredging forms such an 

 infinitesimal fraction of the whole, that it seems superfluous to 

 consider the horizontal distribution of Brachiopods. A few facts 

 may, however, ]3e mentioned. Certain species, as Terebratula 

 vitrea, T. ccqnd se7ye7itis, Walclheimia cranium, Megerlia trv.n- 

 cata, and Discinisca atlantica have a very wide if not cosmo- 

 politan distribution. The second of the above named extends as 

 far north as Spitzbergen, and as far south as Kerguelen Island. 

 Many species are, on the other hand, very localised, and have 

 hitherto only been found in one place. A very considerable 

 number of these have l^een dredged off Japan and Korea, and 

 this region may be to some extent regarded as the headquarters 

 of the group. 



The following species have been obtained within the limits 

 of the British Area, as defined by Canon Norman, who has been 

 good enough to revise the list, which is founded on that drawn 

 up by Davidson in his Challenger Eeport. Their range of bathy- 

 metric distrilnition is given in the column on the left. 



Deptli in 

 Fathoms. 



to 1180. Tcrchratiilina caput serpentis Lin. . Oban, and off Cumbrae Islands, 



Loch Torridon, Scotland, off 

 Belfast 

 8 to 25. Terebratula {Givynla) ca2)sula Jefi'. . Belfast Ba}', E. and S. coast of 



Ireland, Plymouth, Weymouth, 

 and Guernsey 

 5 to 690. Waldheimia cranium Miiller . . . North British seas. Off Shet- 

 land 

 75 to 725. Waldheimia septigera Loven . . . North British seas. Off Shet- 

 land 

 20 to 600. Terebratella spitzbergenensis DsiV. . . N.N. W. of Unst, Shetland 

 18 to 364. Argiope decollata Chemnitz . . . Two miles east of Guernse}' 

 20 to 45. Cistella cistellula S. "Wood .... Shetland, near Weymouth, S. 



coast of England 



650 to 1750. Atrctia gnomon Jeff. W. of Donegal Bay in 1443 



faths. Between Ireland and 

 Eochall, in 1350 faths. 



