NATURAL SCIENCES OF PHILADELPHIA. 139 



base of the middle. The tail is very long, exceeding that of anglorum, which 

 is a much larger species. It is also so very much graduated as to be almost 

 cuueate, the lateral feathers being relatively shorter than in any other spe- 

 cies. The under tail coverts are very long, fully equalling the central rec- 

 trices. 



Color. The upper parts are of a hue quite different from that of anglorum, 

 the black having every where a quite appreciable grayish or plumbeous tinge, 

 and the borders of the feathers being still notably lighter, especially on the 

 scapulars and tertials. The color is deepest on the rump and upper tail cov- 

 erts ; it is much restricted on the sides of the head and neck, not extending 

 below the level of the eyes, and even there its borders are marbled with 

 white. On the sides of the breast the dark color extends considerably more 

 towards the median line, but it is of a very light plumbeous tint, and much 

 variegated with white. Both eyelids are more or less white, and there is, 

 moreover, an indication of a white superciliary streak. The remiges and rec- 

 trices are colored, as in anglorum. The under parts, from the chin to the un- 

 der tail coverts, are white, as are the axillary feathers and inferior alar 

 tectrice.-, the white only interfered with over the flanks by leaden black. The 

 longest posterior under tail coverts are brownish black, as are also one or two 

 rows of the exterior ones, the rest being white, with or without a plumbeous 

 tint. Notice that in amount of white on the under tail coverts, obscurus is 

 just intermediate between anglorum and my new opisthomelas. The bill is 

 deep leaden blue, darker at the apex ; the legs and feet colored, as in anglo- 

 rum. 



Dimensions. Length of bill along culmen, l - 25 ; along rictus, 1-70; from 

 end of nostrils to tip, *90 ; from feathers on side of lower mandible to its apex, 

 1-20; its depth at base, -40 ; width, -35 ; depth at convexity of unguis, -25. 

 Wing, from the carpal joint, 8*00. Tarsus, 1-60 ; middle toe" and claw, 1-80 ; 

 outer do., 1*85. Central tail feathers, 4-25 ; exterior feathers nearly an inch 

 shorter. Total length from tip of bill to end of tail about 11*00 ; expanse of 

 wings about 25-50. 



Variations. I find the differences in size to be about the same, relatively to 

 its dimensions, as in the other smaller Paffini, while, as usual, the general 

 form and the proportion of parts are pretty constantly preserved. The char- 

 acteristic hue of the upper parts is always recognizable, but the precise tint 

 varies with the age of the feathers. The margins of the dorsal tVathers are 

 frequently very conspicuously lighter. The limit of the extent of the dark 

 color on the sides of the head, neck, and breast, hardly differs notably, even 

 with age, and is a strong specific character. The relative amount of the black 

 and white on the under tail coverts is also pretty constant, being intermediate 

 between anglorum and opisthomelas, as before stated. The unusual graduation 

 of the tail is. I believe, always preserved in mature birds. 



The combination in this species of its small size, the tint of the upper parts, 

 and its characteristic line of demarcation with the white on the sides of the 

 head, neck, and breast, together with the color of the under tail coverts, and 

 the length and shape of the tail, renders it readily diagnosticable. As with 

 anglorum, I have taken it as the standard in treating of the other closely 

 allied ; and the peculiar points wherein each differs from it will be found de- 

 tailed under their respective headings. 



Pr/FFi>'us opisthomelas Cones, nov. sp., 



Diag. P. Puffino obscuro nee perdissimilis ; sed major, rostro longiore, 

 robustiore, alis pedibusque longioribus, cauda, breviore, minus rotundata ; 

 et tectricibus caudse inferioribus fere omnino fuliginoso-nigris. 



Habitat. South Pacific coast of North America. 



Description. Form: The bill is rather long, about four-fifths the tarsus, 

 stout, moderately compressed, a wry little higher than broad at the base, the 

 unguis large and strong, its convexity great, and rising much above the level 

 of the rest of the culmen, the depth of the bill at the point of the greatest 



1861.] 



