MANUAL OF NATURAL HISTORY. 51 



lamellar plates or serrated ; tarsi generally 

 short ; toes connected by a membrane, hind 

 toe free. 



2. FAMILY. Divers (Colymbidse). Bill generally 



lengthened, compressed, pointed ; tarsi much 

 compressed ; toes webbed or margined by a 

 lobed dilatation of skin ; wings pointed ; tail 

 very short or wanting ; legs placed far back 

 causing the bird to stand erect ; neck slender, 

 and lengthened. 



3. FAMILY. Auks (Alcidse). Bill varying in length, 



often short, sometimes greatly compressed, 

 culmen curved to tip, where upper mandible 

 is slightly prolonged and inflexed ; tarsi 

 short and compressed; toes connected by a 

 web, hind toe generally wanting; legs placed 

 far back compelling an erect position when 

 standing; tail feathers short and stiff; wings 

 small and pointed, sometimes useless for 

 flight ; neck short and thick 



4. FAMILY. Petrels (Procellariidse). Bill rather 



long, straight, compressed, deeply grooved; 

 upper mandible hooked ; nostrils tubular ; 

 tarsi usually shorter than middle toe; toes 

 webbed; wings long and slender. 



5. FAMILY. Gulls (Laridse). Bill of moderate 



length, compressed, culmen straight for half 

 its length, then curved to tip, which is acute ; 

 nostrils lateral, linear, placed about middle 

 of bill ; tarsi about the length of the middle 

 toe ; toes connected by a web, hind toe ele- 



D2 



