48 GROTE—THE DESCENT OF THE PIERIDS. [Jan. 5, 
beyond upper angle of the cell. Second anal with distinct fork at 
base. Hind wings with humeral spur pointed, turning toward 
apices. 
This genus is generalized by the fact that 4/1 has not ascended 
radius for any distance beyond cross-vein, and that /2 is in origi- 
nal position. It agrees in these characters with the following. It 
is peculiar by the sharp apices. On both wings the discal cross- 
vein between 472 and JZ3 is somewhat weakened and J/2 appears 
continuous in consequence. I can see no indication that the genus 
is Anthocharid, as assumed by Reuter. 
Gen. /dmais Boisduval, 1836. 
Type: I. chrysonome. 
Ldmais vesta. 
I have been unable to obtain the type. The present species 
shows a form quite agreeing with Zeraco/us, differing only that the 
lower part of the cross-vein on secondaries joins the point where 
Mi and J/2 furcate; this position of the cross-vein in Zeraco- 
Jus joins M2 beyond the furcation. Hind wings with humeral 
spur as in Zeracolus. Both these genera are more generalized than 
Leurymus (Colias) by the well-developed humeral spur, the second 
radial not advanced, J4/1 not ascending radius. They may thus 
be regarded as ancestral types of Hurymus. 
This genus may be regarded as more specialized than Zeracolus; 
on account of the disposition of the discal cross-vein. 
We may now turn to the line in which the wings are angulated 
and of an unusual, somewhat leaflike shape, in which the agency of 
mimicry has been suspected. 
Gen. Colas Fabricius, 1807. 
Type: C. rhamni. 
Colias rhamni. Mitt. a. d. Roem. Mus., 8, Taf. ii, Fig. 8 (neura- 
tion). 
The costal region above the cell is wider than usual and the sub- 
costal and radial branches are somewhat bent upwards to sustain it. 
Radius four-branched ; Ar and 2 apparently in original posi- 
tion above the cell, a little further apart than usual. 7/1 ascends 
radius for but a brief space; 4/2 radial. Second anal with a 
strong fork at base. Hind wings with humeral spur vanished ; dis- 
