1900.] GROTE—THE DESCENT OF THE PIERIDS. AT 
Discal cell closed ; J4/1 has ascended radius for nearly a third of 
the distance between cross-vein and external margin; J/2 strongly 
radial. On hind wings the humeral spur has entirely vanished and 
seems to have left no traces; J/2 from cross-vein. 
This is a specialized form from the above characters. Its ally, 
£. edusa, is figured PRoc. AMER. PHILOS. Soc., xxxvii, Pl. ii, Fig. 
8, and the neuration discussed. This genus is known in literature 
as Colas ; I follow Mr. Scudder in retaining Co/as for the type C. 
rhamnt. 
Gen. Zerene Hiibner, 1816. 
Type: Z. czsonia. 
= Meganostoma Reakirt, 1863. 
Zerene cesonia. PRoc. AMER. PHILOs. Soc., xxxvii, Pi. ii, Fig. 9 
(neuration). 
This type can be used as representing a close antecedent stage of 
Eurymus, one through which #wrymus has passed. The dog’s 
head pattern is then a generalization of the pattern of EHurymus, 
and this would be borne out by /d@mazs, in which it is yet more 
developed and which represents a still earlier phase of these two 
genera. The second radial branch stops at the cross-vein in Zerene, 
assuming the 77ifurcula position. On hind wings a fragment of 
the humeral spur remains, the tip being worn away. 
I formerly referred Zerene as = Colas Auct. nec Fab., which 
seems to have been indeed Hiibner’s intention, who, however, also 
included this type (ce@sonta). Mr. Scudder has corrected me (His- 
torical Sketch, 213). 
The preceding types show f2 ina state of flux. In the follow- 
ing it retains its original position above the cell and the types are 
accordingly more generalized. I have my doubts whether a linear 
succession here displays their true affinities, but they are at least 
correctly placed with regard to the degree of specialization of the 
wings. 
Gen. Zeracolus Swainson, 1832. 
Type: T. subfasciatus. 
Teracolus subfasciatus. 
Primaries with sharp apices ; radius four-branched ; Ar and R2 
in original position above cell; #3 a moderate furcation out of 
#4-++ 5 to tip of wing. Discal cell closed ; Mz out of radius just 
