2484 CRUSTACEA. 





New Hebrides, 74°-83°. 

 New Caledonia, 73°-82°. 

 Kingsmills, 80°-88°. 

 Feejees, 74°-85°. 

 Tongatabu, 74°-82°. 

 Samoan Islands, 74°-85°. 

 Tahitian Islands, 74°-83°. 

 Hervey Islands, 68°-76°. 



Hawaiian Islands, 68°-83°. 

 Island of Hawaii, 72°-83°. 



NEW HOLLAND, ETC. 



Port Jackson, 55°-71°. 

 Hobarton, Van Dieniens Land, 50°-60°. 

 Bay of Islands, N. Z., 54°-67°. 

 King George's Sound, 58°-68°. 



A great service will be conferred on science when an isothermal 

 chart for the continents is made out, with the most convenient sub- 

 divisions for illustrating the subject of the geographical distribution of 

 land and fresh-water species. Dove's charts contain in part the ele- 

 ments as regards temperatures ; but it remains to be decided which 

 isothermal boundary lines had best be adopted for this particular 

 purpose ; and moreover, the actual curves of the isothermals dependent 

 on the elevations of a country should be laid down. The winter lines 

 of 68° and 74° for the ocean and air, appear to correspond very nearly, 

 and the same lines might be used for the land chart as well as the 

 marine. The former is the limit for the Cocoanut Palm as well as 

 for coral-reefs, and the Torrid zone of oceanic temperature, might 

 hence be called the Cocoanut-palm as well as the Coral-reef zone. 



Temperature at depths. — With respect to the change of temperature 

 as we descend in the ocean, we cannot present a series of facts, as 

 those that have been ascertained are too few and isolated to be of 

 much service. The lowest temperature reached is 39 i° F., which is 

 less than that of the Frigid Region, as here laid down. Under the 

 equator this temperature is not reached short of seven thousand feet, 

 and somewhere between the parallels of 45° and 60°, the position 

 varying with the seasons and meridian, it is found at the surface as 

 well as at all depths below. 



It is a question of much interest, how far temperature influences 

 the range of zoological species in depth. From a survey of the facts 

 relating to coral-zoophytes, the author arrived at the conclusion, that 

 this cause is of but secondary importance.* After determining the 

 limiting temperature bounding the coral-reef seas, and ascertaining 



* Exped. Report on Zoophytes, 1846, p. 103 ; and on Geology, p. 97. 



