504 GEOLOGY. 
Eocene Dinoceras, being about the size of the brain in the Indian 
Rhinoceros. In the Pliocene strata of the West, a species of Mas- 
todon is the largest mammal, and although but little superior in 
absolute size to Brontotherium, it had a very much larger brain, 
but not equal to that of existing Proboscidians. The Tapiroid 
_ ungulates of the Eocene had small brain cavities, much smallet 
than their allies, the Miocene Rhinocerotide. The Pliocene rep- 
resentatives of the latter group had well developed brains, but 
proportionally smaller than living species. A similar progression 
in brain capacity seems to be well marked in the equine mammals, 
especially from the Eocene Orohippus, through Miohippus and Ar- 
chitherium of the Miocene, Pliohippus and Hipparion of the Pie 
ocene, to the recent Equus. In other groups of mammals, likewise, 
so far as observed, the size of the brain shows a corresponding M- — 
crease in the successive subdivisions of the Tertiary. These facts . 
have a very important bearing on the evolution of mammals, and — 
open an interesting field for further investigation. 
Derr Sea Sounpines. — The “ Tuscarora,” Commander Belk- 
nap, duly reached Honolulu from San Diego, California, having been . 
engaged in taking deep-sea soundings. She made a straight ah : 
sage, not deviating twenty miles on either side of a direct 
drawn between the two ports. During the passage sixty- , 
soundings were made, at a distance of forty miles apart. , 
deepest sounding — the forty-ninth after leaving the coast—"® 
found to be 3,054 fathoms, while the mean depth was 2,562 wai a 
oms. At a distance of 600 miles from the American piney: a 
depth was found to be 494 fathoms, and at 1,050 miles, pe a 
oms. The average temperature below 1,200 fathoms er: B 
to be about thirty-five degrees Fahrenheit. From Honol ” ] 
Japan sixty casts were taken at intervals of about 50 miles. 162 l 
the first 95 miles from Honolulu, the depth increased at “a J a 
ft. to a mile, reaching 2,418 fathoms in lat. 21° N., long. 1 a 
W. The average depth of all the casts taken during thi which 
was 2,450 fathoms. Between the mountains (all but one s ie 
are entirely submarine) the bed of the ocean was very ie os a 
gep depth was found at lat. 22° 44' N., long. 168 m 
3262 fathoms. ; 
Bottom temperatures, as in other parts of the Pacific, = : 
from 33°-2 F. to 34°°6 below 1,800 fathoms, whatever ao 
