TETRAONIDiE.] OSTEOLOGIA AVIUM- [TeTRAONINjE, 



an elongated strip between the nasal ones. Lower rnaxillaries with a very large 

 foramen, and much elongated by a spine projecting from the lower part of its hinder 

 edge. 



Sternum. The body or central part very narrow, with two very large foramina on each 

 side, the first or innermost bounded by a long strip of bone extending almost as far back- 

 wards as the hinder margin of the sternum, expanded at the tips both upwards and 

 downwards, and continued forward nearly to the junction of the ribs, until it joins 

 another strip of bones forming the boundary of the outer foramen, which is also 

 expanded at the tips, and pointed upwards. Manubrial process very large and broad, 

 not bifurcate, truncated at the anterior extremity ; keel very deep, slightly rounded on 

 its lower edge, and curved inwards on its anterior edge, which for one-half of its length 

 has a channel proceeding from the manubrial process. 



Pelvis broad ; obturator foramina very narrow, with another small rounded one at 

 its terminus under the cotyloid cavity, and divided from it by a slight strip of bone ; 

 the ilium projects considerably over the ischium, particularly behind the acetabulum ; 

 there is a very deep indentation on the upper surface at about one- third of its length 

 between the ilium and the sacral vertebra?, in the same situation that a foramen exists 

 in some species of PterocUs. 



Ribs of moderate strength ; styliform process rounded at the extremity. 



Furculum of moderate strength, with a very large triangular process at the junction 

 of the rami, truncate at the lower extremity, and with the sides compressed. 



Coracoids of moderate length, with a rounded process on the outside at their 

 proximal extremities, beyond the articulation with the sternum. 



Scapula strong, slightly arched ; expanded at the hinder extremity, which is blunt, 

 and slightly rounded. 



Leg-bones of moderate size. 



Metatarsus with a large calcineal bone extending to the accessory metatarsal bone, 

 which is slightly twisted on its axis, but not so much as among the pigeons. Tetrao 

 saliceti, T. sioticus, T. tetrix, T. cupido, and Islandorum are all very similar in structure. 



Measurements. 



Tenths. 



Length of humerus 38 



Length of ulna . . 37 



Length of metacarpus 18 



Length of femur "32 



Length of tibia 40 



Length of metatarsus 22 



Length of sternum ...... 49 



Tenths. 



Breadth of posterior margin of sternum 22 

 Breadth of anterior margin of sternum 1 8 



Depth of keel 16 



Length of head . 32 



Breadth of head 14 



Length of pelvis 51 



Breadth of pelvis 27 



Illustration. 



Plate I. H. Skeleton. 



163 



