J. D. Dana on the Classification of Mammals. 67 
Mostracans, al 
the principle 
on as In the range of orders. ; : ; 
‘ne '§ connection of cephalization with rise of rank is also illus- 
jan abundantly in embryonic development. It is one of the 
ental principles in living nature.’ : ie 
is th hen then, in a group like that of Mammals, in which two 
nape Prevailing number of pairs of locomotive organs, there is a 
oe — of the anterior of these two from the locomotive to the 
Phalic Series, there is evidence, in this exalted cephalization 
: Tn his Manual a ag > . 
> of Geology, just published, the writer, speaking of the ancient 
enol, has preferred to nor ihe eet vertebrated tails rather than heterocercal, be- 
an characteristic of a prolonged vertebral column is a of inferiority of 
Was an ae i and the disa of it, in the rs era, 
; ce of that abbreviation of the posterior extremity connected with a rise 
— It is well exemplified, ae. as Agassiz has made in the er thnd 
wis. the modern Ganoid, the young having a vertebrated upper lobe of the 
tebeated. oot before reaching the adult size. Another reason for using the term ver- 
ones sn? hat in some of the ancient Ganoids with vertebrated tails the vertebral 
is central in the tail, and the form is therefore not at all heterocercal, 
ip = 
a. 
