430 PICIDZ. 
development of the red colour is concerned, of which 8. nuchalis is the intermediate 
between it and S. varius. 
3. Sphyropicus thyroideus. 
Picus thyroideus, Cassin, Pr. Ac. Phil. 1851, p. 349°. 
Sphyrapicus thyroideus, Baird, Birds N. Am. p. 106”. 
Sphyropicus thyroideus, Baird, Brew., & Ridgw. N. Am. Birds, ii. p- 547°; Hargitt, Cat. Birds 
Brit. Mus. xviii. p. 196%. 
Picus williamsoni, Newberry, Pac. R. R. Rep. vi. p. 89, t. 24. fig. 1°. 
Sphyropicus williamsoni, Baird, Brew., & Ridgw. N. Am. Birds, ii. p. 545 °. 
Supra niger, dorsi plumis striis celatis albis notatis, uropygio pure albo ; vitta postoculari elongata utrinque 
apud nucham tamen vix conjuncta, altera a naribus infra oculos albis; gutture et pectore nigris, illo 
plaga elongata media a mento coccinea; abdomine flavicante, hypochondriis et tectricibus subalaribus 
nigris albo variegatis ; alis nigris, tectricibus mediis et majoribus plerumque albis, remigibus extrorsum 
nigris, mediis in pogonio externo sparsim albo maculatis, omnibus in pogonio interno maculis albis 
(apicibus exceptis) in margine notatis; cauda omnino nigra; rostro et pedibus nigricantibus. Long. tota 
circa 8:8, ale 5:5, caude 3:5, rostri arictu 1°15, tarsi 0°75, dig. med. absque ungue 0°56, dig. ext. 0°6. 
(Descr. maris ex Refugio, Chihuahua, Mexico. Mus. nostr.) 
@ fere omnino diversa. Supra (pileo fusco-brunneo et uropygio albo exceptis) nigra undique fusco-albido 
transversim fasciata, alis quoque similiter fasciatis, gula media et regione parotica pileo concoloribus, gulz 
lateribus nigro striatis, pectore plaga mediana rotunda nigra ornato; pectoris lateribus, hypochondriis et 
tectricibus subcaudalibus sicut dorsum fasciatis, abdomine medio flavicante; cauda nigra, rectricibus duabus 
mediis in pogoniis ambobus albo fasciatis, fasciis, haud concurrentibus ; rostro et pedibus nigricantibus. 
(Descr. feminz ex Sierra de Bolafios, Mexico. Mus. nostr.) 
Av. juv. plagam pectoralem nigram caret. 
Hab. Nortu America, Rocky Mountains to the Pacific coast °.—Mexico, Pinos Altos 
(Buchan-Hepburn), Jesus Maria, Casa Colorada, and Refugio in Chihuahua 
(W. Lloyd), Sierra de Bolafios (W. B. Richardson), 'Tinguindi near Guadalajara 
(Dr. A. C. Buller, in Mus. Rothschild). 
The female of this remarkable species was described by Cassin as long ago as 1851, 
and the male six years later by Dr. Newberry as a distinct species under the name of 
Picus williamsoni. The relationship of the two birds was not suspected for many 
years, and even in 1874 they were kept distinct by the authors of the ‘ History of 
North-American Birds.’ 
It is now well known that the bird called P. williamsoni is the male and P. thyroideus 
the female of one and the same species. The great sexual difference of plumage in 
this species does not occur in any other Woodpecker. 
S. thyroideus, however, is a true Sphyropicus, having, according to Dr. Coues, the 
tongue constructed as in the other members of the genus; its habits and food being 
also similar. 
Until recently the range of this Woodpecker was supposed to be confined to the 
Rocky Mountain region, and thence to the Pacific coast of North America, where it is 
said to keep chiefly to the pine-belt, of which it is one of the characteristic birds. 
Its range into Mexico was first made known to us on the receipt of a male specimen 
