Dana on the Classification of Animals. 321 
of approximation of Reptiles and Fishes, expanded until each 
of its higher classes had representative species, before the inferior 
division of true or typical fishes—Teliosts—came into existence. 
fterwards, in the Cenozoic, the true or typical Birds and Mam- 
mals had their full expansion. 
he Vertebrate type, therefore, not only was not evolved 
along lines leading up from the lower subkingdoms, but was 
not, as regards its own species, brought out in lineal order from 
the lowest upward. The subkingdom has, therefore, most evi- 
dently a separateness and a roundness below, so to speak, or an 
entireness in its inferior limits, which belongs only to an inde- 
pendent system. 
We find in the facts no support for the legs hypothesis 
with regard to the origin of the system of life. 
Art, XXIX.—The Classification of Animals based on the principle 
of Cephahization ; by JAMES D. Dana.—Number I. 
Some of the tribes of animal life. - 
It is essential, first, that the methods or laws of cephalization 
be systematically set forth, that they may be conveniently stud- 
led and compared. The following statement of them is an ex- 
tension of what has already been presented. pa 
As an animal is a cephalized organism, (or one terminating an- 
teriorly in a head,) the anterior and posterior extremities have 
anterior in position to the normal locomotive organs ; the poste- 
ror portion is the rest of the structure. The anterior is emi- 
hently the cephalic portion. The digestive viscera from the 
Stomach backward, and the reproductive viscera, belong as char- 
acteristically to the posterior portion. 
> t 1412, 1855; this Journal, [2], xxii, 14, 
seep iaey lt, eo yaoene 
