The Swifts 



characters are of rather a technical aspect and need some ex- 

 planation. Enlarged figures of heads among the illustrations 

 should be thoroughly consulted. They show portions embracing 

 the combinations of scales that are of the greatest importance 

 — the supraoailar scales — so called becc.use of their covering the 

 area directly above the eye. From the illustrations it will be 

 noted that the supraocular plates or scales are arranged in a 

 in a large, central series, which are bordered on either side 

 by a row of minute scales. The inner row of these 

 small marginal scales, arranged in crescentic form are, among 

 all the species, in a single row. The outer marginal scales, how- 

 ever, may be present in one, two or three rou's, according to the 

 species. Hence we have an important distinction upon which 

 to base a key. The genus has been treated with more detail 

 than Ufa, and a concise, descriptive list of the species follows 

 the key. All complicated phraseology has been carefully omitted 

 from the former, for the writer believes that the beginner should 

 consider a difficult genus like this from a bird's-eye point of view 

 for the most satisfactory results, rather than plunge into a be- 

 wildering mixture of comparisons. 

 The key follows: 



Division A. A row of large supraocular plates, with a 

 single internal border and one external row 

 of small scales. 



Sub-division I. Internal border of small scales extending 



around forward two-thirds only, of cres- 

 centic margin. 



Color phases. — Grayish or brownish, with transverse, 

 dark wavy bands. No complete black 

 collar. Greenish-gray or scales with green 

 centre; traces of black collar on sides of 

 neck. Size large. 



Clark's swift, .S". clarkii. 



Yellowish, with a wide, reddish band on 

 each side; indistinct, brown cross-bars. Size 

 large. banded swift, S. ^osteromus. 



Brown to blackish ; scales spotted with hltie 

 or green, and red. One of the largest species. 

 orcutt's swift, 5. orcuttii. 

 128 



