266 bulletin: museum of comparative zoology. 



long ago pointed out, because it is the only place where the bottom is 

 normally bathed by water varying only a few degrees, either way, from 

 50°. Deeper down the slope the bottom water is constantly colder; 

 nearer the shore it is so for at least part of the year. Along this zone, 

 too, salinity is much more constant than it is nearer the shore, as well 

 as higher, and probably with but little seasonal change. Added to 

 these hydrographic advantages, is the abundant food supply which 

 usually characterizes the contact-zone between warm and cold waters, 

 the importance of which was long ago realized by Verrill (1881). The 

 result is that the bottom fauna of this zone is remarkably rich, both in 

 species and in individuals, and largely of southern origin (Verrill, 1880, 

 1881, 1884b). But its biological advantages are partly compensated 

 for by its dangers, for at least once within the memory of man its 

 inhabitants have suffered widespread destruction, the surface, for 

 some hundred of miles, being strewn with the dead bodies of the tile- 

 fish (Lopholatilus), as so graphically described by Collins (1884) and 

 Verrill (1882, 1884b) and often commented upon by subsequent 

 writers (Murray, '98, Murray and Hjort, 1912, Sumner, Osburn, and 

 Cole, 1913). And at the same time the invertebrate bottom fauna 

 was practically obliterated (Verrill, 1884a, p. 656; 1884b). Verrill 

 believed that this was due to an off shore movement of the cold bottom 

 water on the shelf, under the influence of violent northerly storms 

 which swept the coast during the late winter and early spring of 1882. 

 And whether this was the true cause, or whether an unusual accession 

 of northern, or of abyssal, water was to blame for the lowered tempera- 

 ture observed by Verrill in that year (p. 239), the occurrence serves to 

 illustrate the fluctuations to be expected along the meeting zone of 

 cold and warm waters. And it was evidently not a unique, though 

 no doubt an unusual occurrence, for in July, 1884, the Albatross 

 encountered great numbers of dead cephalopods floating on the sur- 

 face, over the 100 fathom curve, further south (Lat. 37° 47', Tanner, 

 1886). Conversely the failure of various northern littoral animals to 

 extend their ranges beyond Cape Cod, is probably due to the excessive 

 summer warming, partly due to solar heat, but also to sporadic flood- 

 ing by Gulf Stream water. 



