the Geographical Distribution of Marine Species. 163 
January and February (swmmer months), found the sea-tempera- 
ture 85° to 88° F., near Fakaafo, in latitude 10° south, and longi- 
tude 171° west. In latitude 5° south and the same longitude, 
on the 16th of January, the temperature was 84°; in th, 
January 10th, it was 83° F.; on March 26th, in 5° south, and 
longitude 175° east, the temperature was 86° F. ; on April 10th, 
in the same longitude, under the equator, at the Kingsmills, the 
temperature was .; on May 2d, at 5° north, longitude 
174° east, 834° F.; May 5th, latitude 10°, longitude 169° east, 
82° F. The fact that the region of greatest heat in the Middle 
‘Pacific is south of the equator, as it has been laid down by differ- 
ent authors, is thus evident ; the limits of a circumscribed region 
of hot waters in this part of the Pacific, were first drawn out by 
Captain Wilkes. 
Another Supertorrid region may exist in the Indian Ocean, 
about its northwestern portion; but we have not sufficient in- 
formation for laying down its limits. 
Lsocryme of 74° F.—At San Blas, on the Coast of Mexico, 
Beechey found the mean temperature of the sea for December, 
1827, 74:63° F.; for January, 73:69° F.; for February, 72-40° 
EF. The line of 74° EF. commences therefore a degree or two 
south of San Blas. In the winter of 1827 on January 16 to 18, 
the temperature of 743° to 74:-6° F. was found by Beechey, in 
16° 4’ to 16° 15/ north, 182° 40’ to 135° west ; and farther west, 
in the same latitude, longitude 141° 58’ west, the temperature 
was 74-839 F. West of the Sandwich Islands, near the parallel 
of 20° north, the temperature rises five degrees in passing from the 
meridian of 165° west to 150° east, and the isocryme of 74° F., 
consequently trends somewhat to the north, over this part of the 
ocea tween the meridians of 130° and 140° east, the tem- 
perature of the sea is quite uniform, indicating no northward flex- 
ure; and west of 130° east, nearing China, there is a rapid de- 
Crease of temperature, bending the line far south. Vaillant of the 
Bonite, found the sea of Cochin China, in latitude 12° 16’ north, 
109° 28’ east, to have the temperature 74-12° F'.; and even at 
Singapore, almost under the equator, the temperature on February 
7 to 21, was 77:54° to 79:34° F. The isocryme of 74° F 
poe bass therefore upon the southeastern coast of Cochin 
shina. 
Lsocryme of 68°—Off the Gulf of California, in 25° north, 1179 
west, Beechey obtained for the temperatue of the sea on Dec 
ber 13, 65° F'.; on December 15, in 23° 28’ north (same latitude 
with the extremity of the peninsula of California), 115° west, a 
temperature of 69°41° EF. The line of 68° will pass from the ex- 
tremity of this peninsula, the temperature of the coast below, as it 
is shut off mostly from the more northern or cold waters, being 
much warmer. The temperature 69°41° in the middle of De- 
