176 Bulletin American Museum of Natural History. [Vol. XXXVI, 



etc., are to be considered in reaching a conclusion regarding the status of 

 any form. 



To express within the narrow Hmitations permitted by trinomial nomen- 

 clature what we believe to be the facts in the case should, in my opinion, 

 be our first object; and I consequently have classed as subspecies (1) all 

 representative forms whose intergradation is believed to be proven by the 

 specimens examined; (2) all representative forms whose ranges are not 

 separated by faunal or physical barriers, and which exhibit differences of 

 a racial character; (3) all representative forms whose ranges are separated 

 by physical or faunal barriers but which exhibit such slight differential 

 characters that they may intergrade by individual variation; (4) all repre- 

 sentative forms whose ranges are separated by physical or faunal barriers, 

 which do not intergrade by variation but which are apparently so closely 

 related that they might, with reasonable certainty, be expected to intergrade 

 were their ranges continuous. 



The first group calls for no comment. The second contains by far the 

 larger number of cases in which the trinomial designation is employed. 

 Degree and nature of difference, and proximity of known ranges are usually 

 the determining factors here, and any opinion reached must depend upon 

 the weight given to them. 



No one, for example, comparing specimens of the Andean forms of 

 Pyroderus scutatus, would doubt their subspecific status. Pyroderus 

 scutatus orenocensis is found in western Venezuela, P. s. granadensis in 

 eastern Colombia, P. s. occidentalis in western Colombia, and P. s. masoni 

 in eastern Peru. The species has not yet been recorded from Ecuador, but 

 the close resemblance of the Peruvian race to the more northern races, in 

 connection with the possibility of their geographic contact, leaves small 

 doubt of their intergradation and they are, therefore, ranked as subspecies. 



It is when we come to a nomenclatural expression of the relationships 

 of these Andean forms with Pyroderus scutatus scutatus, that systematists 

 disagree. This bird inhabits the forests of southeastern Brazil and eastern 

 Paraguay. It has never been recorded from the region lying between its 

 known range and that of P. s. masoni of eastern Peru, and the character of 

 the intervening country leaves little doubt that it does not occur there. 



From P. *. granadensis of eastern Colombia, P. s. scutatus differs only 

 in size. It measures, wing, 242; tail, 163; culmen, 40 mm., as compared 

 with wing, 240; tail, 150; culmen, 35 mm., in granadensis. If the birds 

 came from adjoining ranges of the Andes, no doubt would be entertained 

 of their intergradation, but although separated in size by only a few inches, 

 in space they are some 4000 miles apart. It is the latter fact which has led 

 to their recognition as different species, rather than as representatives of 

 one species which they unquestionably are. 



