6o Getteral Notes. [January 



distinct groups, each distinguished by a particular style of coloration, and 

 composed of two species, Ofie of ivhich is an almost exact miniature 

 of the other. This curious, and so far as I know unparalleled, case may 

 be illustrated by the following tabular statement: — 



Group I. Color above, bluish plumbeous; throat and collar round neck, 

 white; a plumbeous pectoral band, behind which there is more or 

 less of rufous, at least in the female. 

 Larger species, C. torquata (Linn.). 

 Smaller species, C. alcyon (Linn.). 

 Group 11. Color metallic bottle-green above, the throat and nuchal col- 

 lar, white ; a bottle-green pectoral band, behind which there is 

 more or less of rufous in the female. 

 Larger species, C ajnazona (Lath.). 

 Smaller species, C americana (Gm.). 

 Group IIL Color above, metallic bottle-green, the throat and nuchal col- 

 lar, orange-ochraceous ; lower parts rich orange-rufous, the male 

 with a pectoral band of white and dark-green bars. 

 Larger species, C tnda (Linn.). 

 Smaller species, C. stiperciliosa (Linn). 

 The curious nature of the case involves several other facts which may 

 furnish rich material for investigation to those engaged specially in the 

 study of the origin of species and the various problems connected there- 

 with. 



In the first place, the difterence between the "homochroniatic" species 

 (if such a term may be used for those resembling one another in color), 

 decreases in regular ratio from Group I to Gi'oup III; in other words, 

 while the difference in coloration between C. torquata and C. alcyon is 

 very marked (so far as the lower parts are concerned), the differences of 

 coloration between C. tnda and C. superciliosa are confined to the merest 

 details ; while C amazona and C. ainericatia differ from one another less 

 than do the species of Group I, but more than those of Group III. 



Scarcely less curious is the circumstance that between the largest species 

 of Group I (C. torquata)., which for size may be compared with an Ivory- 

 billed Woodpecker, and the smallest of Group III, which is scarcely larger 

 than a White-bellied Nuthatch, there is a regular gradation in size, the 

 species standing thus, in the order of their relative dimensions. 

 C. torquata, \n,^^^^^ 

 C. alcyo7t., } 



C. amazona., -\ 



^ . \ Group II. 



C americana. J 



C inda, -i 



r- J. -T \ Group III. 

 C superciliosa, J 



As another noteworthy fact, it may be stated, however, that 2 and 3 on 



the one hand, and 4 and 5 on the other, are more nearly equal in size than 



are i and 2, 3 and 4, or 5 and 6. — Robert Ridgway, Washington. D. C. 



