THE ENDOSKELETON 



703 



other forms of reptiles, the procoracoid usually is reduced, and the 

 clavicle takes its place, though in the lizards, the procoracoid still re- 

 mains in its reduced condition. Clavicles may or may not be present in 

 turtles. If they are, they are represented by the epiplastron (Fig. 417), 

 which is an element of the carapace. In the chameleons and crocodiles 



Fig. 418. A. The skeleton of a rabbit. 



acr., Acromion ; cd.t., condyles for tibia ; cm., calcaneus ; cn.c., cnemial crest ; 

 fe., shaft of femur ; fi., fibula ; g. t., great trochanter ; gr.t., premolar and molar 

 teeth ; h., head of humerus, fitting into glenoid cavity ; hu, shaft of humerus ; 

 il., ilium ; inc., upper incisor teeth of the left side ; ind., lower incisor tooth ; is., 

 ischium; ju., jugal bone ; lac., lacrymal bone; mcr., metacromion ; mx., maxilla; 

 o.f., obturator foramen ; ol., olecranon process ; os., orbitosphenoid bone ; pa., knee- 

 cap ; pis., pisiform bone ; pu., pubis ; ra., radius ; sc., scapula ; sp.s., spine of 

 scapula ; st., sternum ; st.r., sternal ribs ; sup., suprascapula ; .3, third trochanter ; 

 ti., tibia ; tro., trochlea ; ul. ulna ; v.cd., v.cer., v.l., v.sac., v.th., caudal, cervical, 

 lumbar, sacral, and thoracic regions of the backbone ; v.r., vertebral ribs ; x., xiphi- 

 sternum ; x.c., xiphoid cartilage ; II, foramen for optic nerve. The clavicle and 

 hyoid are not shown. 



B. The skeleton of a pigeon, seen from the left side. 



c.r., Fixed cervical rib ; c.r 1 ., free cervical ribs ; cl., clavicle ; cor., coracoid ; d., 

 dentary ; Eu., Eustachian tube ; e.oc., exoccipital ; f.r., fenestral recess ; fe., femur ; 

 fi., fibula ; fr., frontal ; hu., humerus ; i.o.s., interorbital septum ; il., ilium ; is., 

 ischium ; lac., lacrymal ; me. 1-3, metacarpals ; mt. 1-4, metatarsals ; n., nasal ; o.f., 

 obturator foramen ; pa., patella ; par., parietal ; ph. 1-4, phalanges ; pi., palatine ; 

 pm., premaxilla ; p.c.p., postorbital process of frontal ; pt., pterygoid ; pu., pubis ; 

 pyg., pygostyle ; q., quadrate ; r.c., radial carpal ; ra., radius ; s.o.b., suborbital bar ; 

 s.oc., supraoccipital ; sa., supra-angular ; sc., scapula ; sq., squamosal ; st., sternum ; 

 st.r., sternal ribs ; ti., tibia ; u.c., ulnar carpal ; u.p., uncinate process ; ul., ulna ; 

 v.cd., caudal vertebrae ; v.r., vertebral rib ; x.p., xiphoid process ; zy., zygomatic pro- 

 cess of the squamosal ; J., II., foramina for first two cranial nerves ; 1-3, first three 

 cervical vertebrae. (From Borradaile). 



