^^ CALLISTE VIEILLO TI. 



VIEILLOT^S TUEQUOISE TANAGER. 



Tanagra flaviventris . . Vieill. Enc. Meth. p. TJA (partim). 



Callospiza mexicana , . Bp. Compt. Rend. Ac. Sc. Par. xxxii. p. 80 ; Rev. 

 et Mag. de Zool. 1851, p. 169; Note s. 1. Tang, 

 p. 20. 



Calliste vieilloti Sclater, P. Z. S. 1856, p. 257 ; Syn. Av. Tan. p. 83. 



Mas adultus. Niger, capite antico et lateral! cum guttui'e, pec- 

 tore et lateribus necnon dorso postico et tectrieuin alarium 

 majorum marginibus externis ceeruleis : rostri ambitu, torque 

 guttural! interrupto et maculis in lateribus pectoris et ventris 

 nigris : tectricibus alarum minoribus turcoso-cseruleis : remi- 

 gum externarum margine angusta cyanea : abdomine medio 

 cum crisso et tectricibus subalaribus flavis : rostro et pedibus 

 nigerrimis : long, tota 5*4, alee 2 '7, caudse 1*8 poll. Angl. 



Fosmina. A mari vix diversa. 



There can be no question of the fact, however strongly we may 

 uphold the doctrine of the unity of individual species, that, when an 

 animal is extended over a large geographical area, there may be de- 

 tected, as a general rule, certain differences, smaller or greater, as the 

 case may be, between examples coming from two diiferent localities. 

 It is hard to say positively in many of these cases, where local varia- 

 tion terminates and specific difference begins. Some Naturalists are 

 inclined to go very far in one direction, and to look upon many appa- 

 rently well-established species as merely local varieties ; others up- 

 hold the contrary view, and consider the slightest variation in ex- 

 amples from different localities as sufficient for the foundation of 

 new species. In these matters, as in many others, aurea mediocri- 

 tas is the best rule. For myself, however, whilst I am always re- 

 luctant to create new specific titles for animals which can be fairly 

 considered as varieties of established species, I am ever desirous to 

 adopt species where they have been made by other writers, if there 



