ON THE GEOGRAPHICAL DISTRIBUTION 0F CRUSTACEA. 
ut 
By JAMES D. DANA.* 
Is volume xvi, of this Journal, the author presented a chart 
of oceanic isothermal (or rather isocrymal) lines, for the illustra- 
tion of marine zoological geography, prepared more especially 
with reference to the geographical distribution of Crustacea, and 
taken from his Report on the Crustacea of the Exploring Expe- 
dition around the world under Capt. Wilkes. 'l'he following is 
a brief abstract of the remainder of the Chapter on the Distribu- 
tion of Crustacea; the 'T'ables which occupy near 30 pages are 
omitted besides other degjails. 
'T'he lines on the chart, it may be here repeated, are lines of 
equal winter (or coldest month) temperature for the water, the 
*ecold? lines being adopted because the distribution of species 
away from the 'T'ropies.is limited by cold temperature. "'T'he 
temperatures corresponding to the lines are 749, 68? (limiting tem- 
perature of coral reefs), 629, 569, 509, 449, 359 F. Between 
the lines of 68? F. north and south of the equator lies the 7'or- 
rid Zone of oceanic water temperature; from the line of 689 
to that of 359, the T'emperate Zone; beyond the line of 359, the 
F'rigid Zone. 'lhese Zones are divided by the lines into Re- 
gions or Sub-zones as follows. 
I TORRID ZONE. 1. TogRr» REGION ox Sum-zoNE, '/4? and above. 
2. SUBTORRID ke 68? to '149 
IL. TEMPERATE ZONE, 1. WaRM TEMPERATE E 629 to 689 
2. TEMPERATE iH 56? to 629 
8. SUBTEMPERATE E 509 to 569 
4. Corp TEMPERATE jj 449 io 509 
D. SUBFRIGID EE 85? to 449 
HI FRIGID ZONE. 
* From the Author's Report on Crustacea, (2 vols. 4to, 680 and 1620 pages). 
