210 BIKDS OF ILLINOIS. 



ORDER LONGIPENNES THE LONG-WINGED SWIMMERS. 



CHAKACTEKS. Nostrils lateral and perforate, never tubular; covering of the bill simple, 

 or broken only by a sort of imperfect cere (in Stercorariidce). Tip of the maxilla never 

 strongly hooked, often straight Anterior toes webbed. Hallux small and elevated, some- 

 times rudimentary. Basipterygoid bones absent. Palate schizognathous. Carotids 

 double. Eggs several, colored. Young altricial and ptilopaedic. Habit highly volucraL 



The Longipennes are so closely related in their structure to 

 the Limicolce that some systemists unite them in one group*. 



There seems to be no osteological character separating the 

 two groups, except that the Limicolce possess "basipterygoid 

 processes," while the Longipennes do not; and the external 

 differences are chiefly teleological in their character, the Longi- 

 pennes being adapted to a natatorial life, while the Limicolce, 

 with their longer legs and (usually) cleft toes are more waders 

 than swimmers, though some of them, notably the Phalaropes, 

 are as much at home on the surface of deep water as the gulls 

 themselves, 



In both groups, the young, when hatched, are covered with a 

 dense soft down; but those of the Longipennes are reared in the 

 nest, while those of the Limicoloe run about as soon as hatched. 



Three families are recognized, of which two occur in Illinois, 

 their characters being as follows: 



A. Bill with the lower mandible not longer than the upper, and not excessively com- 



pressed. 



1. Stercorariidae. Covering of the upper mandible composed of four distinct pieces 

 a terminal unguis, or hook, two lateral pieces and a cere-like piece saddled upon 

 the culmen, its edges overhanging the nostril. 



2. Laridee. Covering of upper mandible consisting of a single piece through which the 

 nostrils are pierced. 



B. Bill with lower mandible much longer than the upper, both mandibles excessively 



compressed, like a thin knife-blade, for terminal portion. 



3. EynohopidsB. (Extralimital to Illinois.) 



* Gavio-Limicolce: SEKBOHM, The Ibis, Oct. 1888. pp. 431-133. 



