NO. 1010 UFA'IXIOy OF BVT0RIDE8 VIRESCE\S—OBERfIOLSER. 533 



in some examples is dull oily green, in others decidedly bluish vdih 

 a glaucous bloom; also in the depth and shade of the chestnut, ma- 

 roon, or fulvous of the neck and sides of the head. 



The characters which separate tlio various subspecies are largely 

 differences of size, and of the colors of the hind neck, sides of the 

 head, and of the entire lower surface. The color differences of 

 pileum, back, wings, and tail are of very little value in diagnoses, 

 since these are duo chiefly to ago, season, or individual variation. 

 The names of colors used in my descriptions are based on Mr. Robert 

 Ridgway's Nomenclature of Colors.* 



All the measurements in this pai)er are in millimeters. The spec- 

 imens used in the average measurements under each subspecie.-, and 

 which form the basis of comparison, are, just as far as possible, from 

 typical specimens; that is, from examples representing the best dif- 

 ferentiation. In the tables of detailed measurements all the speci- 

 mens used in the diagnostic averages are indicated by a minuscule; 

 and all other than adult birds are noted. The various dimensions of 

 which use is made in the following pages have been taken as follows: 



Length of wing. — Measured in a straight line from the bend of the 

 closed wing to the end of the longest primary with these feathers in 

 their natural position; that is, not straightened. 



Length of tail. — Taken with dividers from the point of insertion of 

 the middle rectrices to the tip of the longest. 



Exposed culmen. — Measured in a straight line from the beginning 

 of the feathers on the culmen to the tip of the maxilla; that is, the 

 chord of the exposed culmen. 



Height of hill. — The distance in a straight line from the base of the 

 exposed culmen to the nearest point on the ramus of the mandible. 



Length of tarsus. — A straight hne from the center of the heel joint 

 on the posterior side to the middle of the joint between the metatar- 

 sus and the middle toe on the anterior side. 



Middle toe. — Measured along the upper side from the middle of the 

 joint between the metatarsus and the middle toe to the base of the 

 uncovered claw. 



BUTORTOES VIRESCENS VIRESCENS (Linnaeus). 



[Ardea] virescens Linn^us, Syst. Nat., ed. 10, vol. 1, 1758, p. 144 (America) 

 (based on "Ardea etellaris niinima," Catesby, Nat. Hist. Carolina, Florida, 

 and Bahama Islands, vol. 1, 1731, p. 80, pi. 80 [Virginia and Carolinji]). 



Ardea chloroptura Boddaert, Tabl. Planch. Enlum., 1783, p. 54 (based on 

 "Crabier de la Louisiane," Daubenton, Planch. Enlum., No. 909; and 

 "Crabier roux a t§te et queue vertes," Buffon, Hist. Nat. des Oiseaux 

 [ed. Deux Ponta], vol. 14, p. 146; orig. ed., vol. 7, 1780, p. 407 [Louisiana]). 



[Ardea] ludoviciana Gmelin, Syst. Nat., vol. 1, pt. 2, 1789, p. 630 (based on 

 "Crabier roux ^ t§te et queue vertes," Buffon, Hist. Nat. dos Oiseaux, 

 vol. 7, 1780, p. 407; "Crabier de la Louisiane," Daubenton, Planch. 

 Enlum., No. 909; "Louisiane Heron," Pennant, Arctic Zool., vol. 2, 1785, 

 p. 448, No. 350; and "Louisiane Heron," L.\tha.\i, Gen. Synopsis Birds, 

 vol. 3, pt. 1, 1785, p. 81, No. 47) (Louisiana). 



> Rldgway, Nomenclature of Colors for Natiirallsts, Boston, 1886. 



