150 VERTEBRATE ZOOLOGY 



of the animal. In the auditory capsule the opisthotic, prootic, 

 and epiotic— all of which are cartilage bones— appear on each side, 

 the epiotic becoming fused with the supra-occipital. The optic cap- 

 sule is entirely membranous. The nasal capsule is cartilaginous, 

 the only bone developing in it being the vomer, a membrane bone. 

 Nasals do not occur. 



Boil the skull until the bones can be separated from one another. 

 Take them apart and examine each carefully, identifying the bones 

 belonging to the various regions of the skull. 



The Appendicular Skeleton; the Anterior Extremities. The an- 

 terior extremities are composed of the pectoral girdle and the fore 

 limbs. The skeleton of the former is made up of three bones on 

 each side of the body,— a cylindrical dorsal bone, the scapula, and 

 the two ventral bones, the procoracoid and the coracoid, the latter 

 being behind the former. The scapula and the procoracoid are con- 

 tinuous, forming a single piece; the distal ends of the ventral 

 bones are joined by a ligament. At the meeting-point of these 

 three bones is the glenoid fossa, the depression in which the hu- 

 merus articulates. 



The foreleg contains three divisions, — a proximal, a middle, and 

 a distal division. The skeleton of the proximal division, or upper 

 arm, is a single bone, the humerus. That of the middle division, 

 or forearm, contains the radius and the ulna ; the former is preax- 

 ial and extends farther distally than the latter. The distal division 

 consists of the wrist and hand. The skeleton of the wrist, or carpus, 

 is made up of nine bones, of which three, the ulnar, intermedial, 

 and radial, form a transverse row at the distal end of the radius 

 and ulna, and five, which are called the carpals, form a row at the 

 proximal end of the hand. The first carpal bone abuts on the 

 radial. Adjoining the ulnar is an additional bone, the pisiform, 

 which differs from the others in that it is a membrane bone, being 

 formed as an ossification in a tendon. It is thought by some to 

 be a rudiment of a sixth finger and is homologous to a similar bone 

 in mammals. 



The skeleton of the hand is made up of five digits, each of which 

 is composed of a single proximal metacarpal bone and several finger 

 joints, or phalanges. 



