426 



ZOOLOGY 



SECT. 



and cut off from the exterior, in the unmacerated skull, by the 

 tympanic membrane, are extremely small bones, which form a 

 chain extending, like the columella auris of the Pigeon, from the 

 tympanic membrane externally to the fenestra ovalis internally. 

 There are three of these auditory ossicles the slopes, which corre- 

 sponds to the columella of the Pigeon ; the incus, and the malleus, 

 with a slender process the processus gro.cilis. In addition there 

 is a small disk-like bone, the orbicular, which is attached to the 

 incus. 



The elements of the pectoral arch (Fig. 1020) are fewer than in 

 the Lizard. There is a broad thin triangular scapula, the base 



or vertebral edge of which has 

 a thin strip of cartilage (the 

 supra-scapular cartilage) con- 

 tinuous with it. Along the 

 outer surface runs a ridge 

 the spine; the spine ends 

 below in a long process the 

 acromion process (a.) from 

 which a branch process or 

 metacromion (ma.) is given off 

 behind. The part of the 

 outer surface of the scapula 

 in front of the spine is the 

 FIG. 1020. Lepus cunicuius. shoulder- prc-spinous or pre-scapular 



girdle with anterior end of sternum of young- /> / ^\ j.1 j.'Ul'J.i-l 



Specimen. . acromion; af. pre-scapular foSSa (/.), the part behind the 



fossa; c. coracoid ; cl. ossified clavicle ; ma. <-nn<if oiW-w^w/c nr mntf ^rftfniilfi^ 



metacromion ; r.isL meso-scapular segment ; pOSt-SpinOUS . pOSl-SCapUiat 



ost. pro-sternum ; pc. pre-coracoid ; pf. post- foSSa (vf.\ At the liaiTOW lower 



scapular fossa ; si: sternal ribs. (After -, ^ , i i 



Fiowero end of the scapula is a con- 



cave surface the glenoid 



cavity into which the head of the humerus fits, and imme- 

 diately in front of this is a small inwardly curved process the 

 coracoid process (c.) which is represented by two separate ossi- 

 fications in the young Rabbit. A slender rod the clavicle 

 (cl.) is connected with the acromion process externally and 

 with the sternum internally by means of fibrous tissue. At- 

 tached to the outer end of the clavicle is a small cartilage, 

 the meso-scapida (mss.) t and connected with its inner extremity 

 are two similar cartilages, which are supposed to represent the 

 ventral portion of the procoracoid (pc.) and the epislernwn of 

 the Sauropsida. 



The skeleton of the fore-limb is more readily comparable with 

 that of the Lizard than with that of the Bird : but there is a 

 difference in the position of the parts owing to the rotation back- 

 wards of the distal end of the humerus, all the segments being 

 thus brought into a plane nearly parallel with the median vertical 

 plane of the body, with the pre-axial border directed outwards, and 

 ,the original dorsal surface backwards. The radius and ulna are 



