J. D. Dana on the Homologies of Insects and Crustaceans. 283 
? 
violence to reason in supposing that the profound movements 
which originated the lofty border-chains of one continent should 
have raat simultaneously (although it may have been very un- 
equally) at the two sides of the oceanic basins, and thus have 
produced world-wide results. If so, we have a universal cause for 
simultaneous universal effects. There is evidence that in the 
case of some of the minor oscillations there were synchronous 
parallel movements in the North American and European con- 
tinents ;—as in the formation of marine limestones alike on the 
vibrations of the crust, surely we may look for synchronous rs 
tains.. T 
In 
that the subdivison of time into Paleozoic, Mesozoic and Ceno- 
zoic should be registered in the strongest lineaments of the 
earth’s surface 
ArT. XXII.—On the Homologies of the Insectean and Crustacean 
Types; by JAMES D. DANA. 
IN a note to the article on cephalization, at page 6 of this 
volume, a brief statement is made by the writer on the relations 
between the structures of Insects and Crustaceans. foll 
. : aisaren and explanations will make the subject more intel- 
gible. 
Cc z A 
3 : | eeemnen Y eerie 1 i 
‘ Se ohio ta te 1s 144546 La iette 20 21 
Coperscnas, 2-14 doe EPP PE ere 
ABR ae Paint cocnloantiae™ Seetncliaiiagtth iii 
: C x A 
iy," 
G 
=e 
"The diagram presents to the eye the succession of normal seg- 
Am. Jour. Sc1.—Srconp Series, Vow. XXXVI, No. 107.—Sxpr., 1863. 
30 ‘ 
