Ridgway.] 74 [May 21, 



The relationship of this well-characterized, and very remarkable, 

 genus, is nearest to Herpetotheres, 1 with which it agrees in osteological 

 structure, besides in essential external features; but it differs from 

 this in some minor points in the external anatomy, and more markedly 

 in the nasal bones, which in the present genus are less completely ossi- 

 fied than in Herpetotheres. It presents analogies with Circus and the 

 StrigidcB in the facial ruff, with the Strigidce in the character of the 

 inner web of the quills, as well as in the dimorphic plumage of some of 

 the species, and with Nisus in its general form and habits. 



Eight species are given in Gray's Hand List (i, p. 31), but of this 

 number only five are tenable. The M. castanilius (No. 295) is a 

 Nisus (see Sclater and Salvin, Exotic Ornithology, pi. 18). M. 

 rujicollis Vieill. (No. 292), with xanthothorax Temm., as a synonym, 

 M. guerilla Cass. (No. 296) and M. zonothorax Caban. (No. 297) are 

 names for different phases of a single species; while No. 294 should 

 stand as concentricus Vieill., the name gilvicollis Vieill. being a syn- 

 onym of M. rujicollis. 



The following synopses include all the valid species of the genus 

 known at the present time ; the first giving the prime specific char- 

 acters, the second giving the sets of characters which distinguish the 

 species. 



The number of tail-bands cannot be relied on as a specific char- 

 acter, since there is a great variation in this respect among different 

 individuals of the same species. Thus, semitorquatus has in some 

 specimens only four bands, and in others as many as seven; rujicollis 

 has four to six; leucauchen has six to seven, and concentricus three to 

 four. The number is greater in the young plumage than in the adult. 



A. — Inner toe appreciably shorter than the outer. 



a. Wing, 9.00 or more. 



1. Black above, with a nuchal collar. Tail longer than 



the wing, M. semitorquatus. 



2. Plumbeous above, without a nuchal collar. Tail shorter 



than the wing, M. mirandollei. 



b. Wing less than 8.00. 



3. Throat and adjoining portions ashy in the adult; no 



nuchal collar, M. rujicollis. 



4. Throat and cresent behind the jaw, white, sharply de- 



fined; a nuchal collar of whitish spots, M. leucauchen. 



iPhysta Vieill., 1816? Herpetotheres Vieillot, 1818. Cachinna Fleming, 1822. 

 Macagua Lesson, 1831. Type Falco cachinnans Linn. 



