726 THE ANATOMY OF THE RUFFED GROUSE 



tened in the sagittal plane and bears several tuberosities, the most anterior of which is large 

 and forms the artirulation with the coracoid. Dorsally. there is a rrest, the crista lateralis, 

 which also protrudes laterally and which serves for the attachment of M. pectoralis thoracicus. 

 Ventrally. there is the tuberculum mediale which contains on its posterior aspect a large fora- 

 men for the entrance of the air duct. The distal end turns a hit laterally and possesses two 

 condyles. 



In the medial division of the wing, the ulna and radius lie roughly parallel. Tlic ulna is con- 

 cave internally and has, on its external aspect, about eight slight tuberosities indicating the 

 points of attachment of the secondaries. The radius is a straight terete bone, slightly out- 

 curved distally, and articulates with the more dorsal of the condyles of the humerus. 



The outer division of the wing consists of those bones distal to the ulna and radius. Digit 

 I is small and its metacarpal is a small block of bone fused to metacarpal II. Digit II is the 

 longest and consists of two phalanges. Its metacarpal is well developed and possesses the 

 characteristic Galline process about one-third the length from the proximal end which is a 

 somewhat flattened spur-like extension, protruding outward over the third metacarpal. Digit 

 III has only one phalanx which is. however, free. Its metacarpal is thin and is fused at both 

 ends to the metacarpal of II, producing a long fenestra. 



Pelvic Girdle and Synsacrum. The synsacrum (figure 77g) is composed of fourteen fused 

 vertebrae, the first of which is really of thoracic origin and bears a jointed floating rib. The 

 first four have their transverse processes fused with the ilium. The last six vertebrae have 

 a thin sheet of bone connecting them with each other and with their transverse processes. 

 As in other grouse and in Gallus, the transverse process of the tenth vertebra is markedly 

 larger than that of the others and there is a perforation between it and the roof of the sac- 

 rum. The ilium is a large pneumatic bone attached to the vertebral column, mainlv by the 

 transverse processes of the vertebrae but also by a thin plate of bone from the internal border 

 of the iliac fossa to the fused spinal processes of the first four vertebrae. The concavitv forms 

 the whole preai ctaliuiar portion of the ilium. The postacctabular portion is flat and is fused 

 laterally with the ischium and extends as a cornice over the region of fusion. Tym panuchus 

 has an extreme development of the ilial cornice so that it completelv covers the ischium. The 

 ischiadic foramen, located inunediately behind the acetabulum, is large and somewhat pointed 

 posteriorly. The obturator foramen is located between the pubis and ischium. The ischium is 

 sharplv pointed posteriorlv. Tlie pubis is slender and is attached for about otie-half of its 

 length to the ischium. Posteriorly, it protrudes beyond tlie ischium and then is directed 

 hiedially. It is much smaller than in Gallus. In Tympanuchus. the transverse processes of the 

 sacral vertebrae are wider, as seen from the under surface, and the anterior portion of the 

 ilium is much broader than in Bonasa. 



Lep. The head of the femur (figure 77h) is a round knob projecting nearly at right angles 

 to the shaft and fitting into the acetabulum of the pelvis. Opposite this is a prominent shoul- 

 der, the trochanter, which extends as a short ridge, parallel to the shaft, on the internal edge 

 of which are several perforations for the passage of pneuniatic ducts. The sliaft is not straight 

 but is slightly convex forward. The distal part is composed of two condyles, the external of 

 which has a small fossa in its anterior aspect. 



Tlie ))atella is a well developed sesamoid bone, lying on the anterior surface of the knee 

 joint. The tibia is a long straight bone, the proximal end of which is considerably expanded 

 and terminates in a broad transverse surface with raised edges, which is indented for the artic- 

 ulation of the condyles of the femur. On the anterior aspect of the proximal end is the cnemial 



