1900.] GROTE-—THE DESCENT OF THE PIERIDS. 41 
radius is only four branched. I have elsewhere discussed the re- 
semblance between 772furcu/a and the present line. 
Gen. Midea H.-S., 1867. 
Type: M. genutia. 
Midea genutia. 
Radius four-branched, hence more specialized than Anthccharts- 
Zegris, and with the second radial removed outwardly to very 
slightly beyond cross-vein, thus belonging to this series. Costa not 
depressed ; apices acuminate between J/1 and J/2; external mar- 
gin retired, sinuate; anal angle of secondaries hardly as prominent 
as in Anthocharis. Mx ascends radius for a little more than one- 
third of the distance from cross-vein to external margin. 
This genus differs from the equaily four-branched Zetracharis in 
the passing of the cross-vein by #2 as well as in the peculiar 
shaped primaries. I cannot admit the validity of the rule under 
which Mr. Scudder rejects this generic name. It is a limitation of 
the law of priority which is not recognized by all zodlogists, and is, 
I think, in itself indefensible. 
I regret not to have had more species belonging to this group for 
examination. The series as arranged by me is not, as I have said, 
ideally perfect. It must be remembered that an existing type rep- 
resents in some main feature a stage, standing between two others, 
which the higher genus has passed through and the lower com- 
mences to exhibit. After the type has been assumed, it will have 
further differentiated not only in the same direction, but, owing to 
the inequality of the specializations, in other directions which bring 
it out of focus. And the parent type has itself changed in the same 
way ; perhaps we can even no longer recognize it as such, perhaps 
it has dropped away forever. 
We now can turn to the generalized type of this series of ‘‘ an- 
gled Whites,’’ one which may stand for the parent of the two lines 
I have indicated and from the ancestors of which they may possibly 
have been thrown off. That we have to go to Chili for this type 
may possibly seem strange, and it may be there is a progenitor or 
its representative nearer home which I have not discovered, but the 
question of distribution is so far-reaching and so little is safely 
known as to its action and causes that I cannot here enter at all 
upon it. I must take the types where I find them. 
