176 



Suborder XV. GA VIJ^. 



Long- winged ' schizognathous birds, with the angle of the mandible 

 truncated, an ectepicondylar process to the humerus, two fcnestrse 

 in the proximal phalangeal of the second digit of the manus, and 

 slight U2)ward extension of the cnemial crest of the tibio-tarsus. 



The skull has well-marked supraorbital grooves, which usually 

 meet in the middle line. 



The legs vary considerably in length, the tarso-metatarsus being 

 short in Sterna and long in Larus. 



The tarso-metatarsus in the typical forms is of considerable length, 

 with an angulated shaft, a large inner ridge to the talon, and two 

 open channels for the flexor tendons - ; the second distal trochlea is 

 shorter than the fourth, and directed somewhat backwardly. 



The tarso-metatarsus is generally long and slender ; its cnemial 

 crest extends but slightly above the head ; the fibular ridge is very 

 short ; the distal condyles are inclined somewhat inwardly (although 

 not to such an extent as in the Anseres), are very short, and have a 

 long inferior surface ; there is no intercondylar tubercle near the 

 extensor bridge. 



The femur is nearly straight, with a tall great trochanter, a very 

 short neck, a slightly expanded distal extremity, in which the outer 

 condyle is the longer, the anterior intermuscular ridge continuing 

 throughout the length of the bone without joining the great tro- 

 chanter '\ and no pneumatic foramen. 



The coracoid is long and nearly straight ; the hyosternal process 

 is narrow and hook-like, and there is a marked and characteristic 

 inflection of the anterior sternal angle ; the intermuscular ridge is 

 slight and approximated to the posterior border ; the subclavicular 

 process is large and plate-like, and the shaft is often perforated at 

 its base * ; the sternal articular surface occupies the whole width of 

 the bone and is but little arched. 



The humerus (fig. 39) is long and slender, with a deep subtro- 

 chanteric fossa devoid of pneumatic foramen, and, in recent forms, 

 another similar fossa for the triceps placed more internally near the 

 head ; there is a deep coraco-humeral groove, passing externally into 



1 The extinct Mijialiornis, if referable to this suborder, is an exception in 

 this respect. 



- In the shorter tarso-metatarsus of Sterna the inner dexor channel becomes 

 a closed tube. 



^ This character distinguishes the femur from that of the Gallina. 



' Milne-Edwards states that this perforation is invariably present ; but it is 

 absent in many recent skeletons in the Museum. 



