AVES. 593 



short, and much hooked ; wiugs long, the second and tliird <iiiills longest ; 

 lai) conical. 



flotus melanogaster. — The Black-Bellied Darter. Plate xxxix**. fig. S. 

 Described, vol. iii. p. 377. 



Genus 20.— PHAETON.— ijren<r!W. 



Generic Character. — Bill longish, thick, strong-, hard, sharp pointed at the 

 edges, greatly compressed, with a slight curvature from its base; edges of 

 botli mandibles widened at their base, compressed, and serrated, from thence 

 to the tip ; under mandible slightly curved, on its lower margin three- 

 fourths its length, and acutely tapering to the point; nostrils near the base, 

 lateral, pervious, and partly concealed by a membrane ; legs very short, 

 strong, placed far back ; three anterior toes, connected to their tips by a 

 membrane; the hallux small, short, placed behind, and free; wings long, 

 first and second quills longest ; tail short, but having two long filamentous 

 central feathers, which are slightly forked. 



Phaeton phtenicur us. — The Red-Tailed Tropic Bird. Plate xxxix**. fig. 

 4. Described, vol. iii. p. 377. 



Genus 21.— COLYMBUS— Xattow. 



Generic Cltaracter. — Bill as long as the head, strong, compressed, acutely 

 pointed, and somewhat cylindrical ; upper mandible longer than the under 

 one ; nostrils situated at the base of the bill, concave, and half-closed by a 

 membrane ; legs placed far behind ; tarsus strong, compressed ; three an- 

 terior toes very long, united to their tips by a web ; hallux short, articulated 

 interiorly, united by a rudimentary membrane ; wiugs of medium length ; 

 the third quill the longest ; tail very short and rounded. 



Colymbus glacialis.— The Great Northern Diver. I'late xlviii. tig. 3. De- 

 scribed, voL iii. p. 397. 



Genus 22. — URIA. — Biisson. 



Generic Character. — Bill of medium size, short in some species, straight, 

 pointed, and compressed ; upper mandible slightly bent towiuds the point, 

 the lower one forming an angle, a little open ; nostrils basal, lateral, concave, 

 oblong, ovate, longitudinal, half concealed by a broad membrane covered 

 with feathers and pervious ; legs short, placed far back ; feet with three 

 anterior toes only, webbed to their points ; wings short, narrow ; first and 

 seiond quills longest. 



I'ria gylle. — The Black Guillemot, Plate xlvii*. fig. 9. Described, vol 

 iii. p. £98, &c. 



Genus 23.— MERGULUS.- ^■iei7/«<. 



Generic Character. — Bill shorter than the head, a little arcuated, conico- 

 convex, a little open between the mandibles ; upper mandible slightly bent 

 towards the point ; low er mandible straight half way from its base, where it 

 forms an acute angle, and suddenly tapers to a point ; base of both mandibles 

 clothed with leathers ; nostrils round, partly covered by the leathers of the 

 capistrum ; legs short, placed far behind; feet with three anterior toes only, 

 united to their points by a web ; claw.> long and sharp ; wings short ; the 

 first and second quills longest ; tail short and pointed. 



