240 INDIAN CYPRINID&. 
appear to be a natatorial type of Sarcoborine, corresponding with that type in 
the order of perching birds. To this however there is some objection, for if the 
Sarcoboriné represent the Fere, the most carnivorous genus of the sub- 
family (which Opsarions would seem to be) ought to represent the Halconide 
in which there is only one genus (Gypaétus) remarkable for short feet and 
great breadth of wing; but the cruel habits and voracious appetite of the 
Opsarions go to establish this last as the true analogy ; this however as well as 
many other points must remain to be decided by further inquiry. In the 
mean time we may be justified in the conclusion that the Mere among the 
Mammalia, and the Falconide among birds have their representatives among 
the Cyprinide, and that the same type in each of the three groups seems 
to possess certain corresponding characteristics which may distinguish them 
from all adjoining groups, and that in describing those characters, the same 
terms are as applicable to the one as to the other, which is quite sufficient to 
prove their corresponding analogies. 
39. It may be objected to by those who have not paid much attention to 
the subject, that detached comparisons of this nature are of little value; still, 
they are important as the means of directing attention to characters that 
would otherwise be liable to be passed over unobserved, I am therefore dis- 
posed to pay little regard to such objections. The number of species and 
groups are now so much multiplied in every department of natural history, 
that detached descriptions are daily diminishing in value ; and, besides, it is so 
easy to make a new genus if not required to shew our reason for doing so, 
that we need not be surprised that it should now have become a regular trade, 
and that many acquire a temporary fame with the unthinking part of man- 
kind by the practice. 
40. The first test of a natural group is the circularity of its contents. 
To ascertain whether the affinities of the Cyprinide are circular, it is 
