the Geographical Distribution of Marine Species. 157 
the latter sinks to 745° F. some parts of the year, 74° F. is taken 
as the limiting temperature. ‘The eejee seas are exceedingly 
prolific and varied in tropical species. The corals grow in great 
luxuriance, exceeding in extent and beauty anything nitacigey 
observed by the writer in the tropics. The n betw 
F., north of the equator, and 74° EF’. south, is siceekate ac seine 
tropical or torrid region of zoological life. 
With respect to the line of 80° F., we are not satisfied that it 
is of much importance as regards the distribution - ee The 
range from the hottest waters of the ocean 88° t °F. is but 
fourteen degrees, and there are probably few a occurring 
within the region that demand a less range. Still, investigations 
hereafter made, may show that the hot waters limited by the iso- 
cryme of 80° include some peculiar species. At Sydney Island 
and Fakaafo, within this hot area, there appeared to be among 
corals a rather greater prevalence than ~ of the genus Mano- 
pora, which as these are tender species, may perhaps show that 
the waters are less favorable for ie corals than those of the 
Feejees, where the range of temperature is from 70° to 80° F. ; 
but this would be a hasty conclusion, without more extended ob- 
servations. The author was on these islands only for a few hours, 
and his collections were afterwards lost at the wreck of the Pea- 
cock, just as the vessel was terminating the voyage by entering 
the Columbia River. 
It is unnecessary to remark particularly upon the fitness of the 
other isocrymals for the purposes of illustrating the geographical 
—— of marine species, as this will become apparent from 
e explanations on the following pages 
The regions thus bounded require, for convenience of designa- 
tion, separate names, and the following are therefore proposed. 
They constitute three larger groups: the first, the Torrid zone 
or Coral-reef seas, including all below the isocryme of 68° F. ; 
the second, the Temperate zone of the oceans, or the surface bee 
tween the isocrymes of 68° F. and 35° F.; the third, the Frigid 
Zone, or the waters beyond the isocryme of 35° 
I. TORRID OR CORAL-REEF ZONE. 
Regi Tsocrymal limits. 
a. Supertori . ~ - 80° FE’. to 80° F. 
rrid, - ~ - 80° — to 749 
3. Sabtotrid, - - - 74° te GRP a 
Il. TEMPERATE ZONE. 
1. Warm Temperate, - - ° to 62° 
2 simone . od) 62> ae 
3. Subtem - - = BGO tebe 
4. Cold Periperste, bee a - 6 6 2s 
5. Subfrigid, - - «it AAO ABS? 
rer 
