THE DEEP-SEA FAUNA. 245 
PANAMIAN, 
{G. willemoesii. §. of Amboina in Banda 
Gnathophausia willemoesii (493-1270 fms.). | Sea (1425 fms.). 
| G. sarsil. Bay of Bengal (102 fms.). 
Ob brevispinis (551-1471 fms.). | Bay of Bengal (690-1748 fins.). 
Eucopia australis (551-1770 fms.). North and Tropical Atlantic; Southern 
Ocean; Antarctic Ocean; Japan; Bay of 
Bengal; Gulf of Manaar (350-2500 fms.). 
Petalophthalmus pacificus (700 fms.). P. armiger. Tropical mid Atlantic (2500 
fus.). 
A study of the deep-sea Crustacea thus leads to the conclusion that this 
fauna is one of cosmopolitan range, indivisible into subordinate local pro- 
vinces like those of the littoral and terrestrial faune. This is what one 
would expect from the uniformity of conditions prevailing at great depths 
and from the enormous length of time that has elapsed since modern types 
of marine Invertebrata came into existence. We have seen not only that 
many of the denizens of the cold waters of the intermediate zone, even with- 
in the tropics, are emigrants from the shallow water of cold and cold-temper- 
ate latitudes, but also that very many of the peculiarly deep-sea types betray 
their kinship with boreal genera. This, in the absence of much light from 
paleontology in this particular group of animals, may afford us the clew to 
the origin of a large part of the abyssal Crustacean fauna. Rarely, as in the 
case of the recent Lryontide, do we find a deep-sea type that vividly recalls 
an ancient form. In this case, so good an authority as Boas thinks that the 
modern deep-water Polycheles is identical with the Jurassic Hryon. It is of 
interest to note that in the same beds at Solenhofen — beds of undoubted 
shallow-water origin— we find with Lyon another singularly antiquated type 
in Limulus. But the surviving descendants of Limulus are pre-eminently 
littoral. It is manifestly illogical to assume, as some have done, that because 
a certain form is now restricted to deep water the rocks in which it occurs 
as a fossil were deposited at a similar depth. The surviving representatives 
of an ancient shallow-water type may be littoral, as in the case of Limulus, 
or they may be found only in deep water, like the recent Hryontide. Some 
unquestionably bottom-living species at the present day have a vertical 
distribution of 2000 fathoms. For instance, Parapagurus abyssorum ranges 
from 250 to 2221 fathoms,* and Dall} states that certain species of Mollusca 
* Not taking into account the “Challenger” record of this species in 45 fathoms off Patagonia 
(Henderson, Rep. Challenger Anomura, p. 89, 1888). 
+ Bull. Mus. Comp. Zodl., XII. 186, 1886. 
