418 THE ANATOMY OF YEETEBRATED ANIMALS. 



muscle ; and, in the absence of a complete clavicle, the outer 

 fibres of the latter and those of the anterior part of the 

 deltoid are continuous. In this way a muscle which has 

 been called levator humeri proprius is formed. The omo- 

 hyoid and the subclavius are absent. There is a trachelo- 

 acromialis and a dorso-epitrochlearis. The supinator longus 

 is absent, but there is a pronator quadratus. The extensor 

 communis digitorum maniis divides into four tendons, in 

 which sesamoid bones are developed over the articulations 

 between the first and second phalanges. The extensor 

 primi internodii polUcis is absent. The extensor secundi 

 internodii is one muscle with the extensor indicis. The 

 extensor minimi digiti sends tendons to the third, fourth, 

 and fifth digits. All these deep extensors have sesamoid 

 bones over the metacarpo-phalangeal articulations. The pal- 

 maris longus appears to be absent ; but all the other flexors 

 of the manus, even the palmaris hrevis, are represented. 

 The tendons of the flexor pollicis longus and flexor digi- 

 torum perforans are united. The divisions which the 

 common tendon sends to the five digits develope sesamoid 

 bones, just before their insertions into the bases of the distal 

 phalanges. The fifth digit has its abductor, flexor Irevis, and 

 opponens; the poHex, an abductor, adductor, flexor hrevis, and, 

 perhaps, an opponens. The second, third, and foiu-th digits 

 have each a pair of flexores breves, which represent the 

 interossei, and are inserted into the bases of the proximal 

 phalanges, a relatively large sesamoid being developed in 

 each. Each sends oif a fine tendon dorsad to the extensor 

 sheath. The plantaris is large, and, as in the Pig, its 

 tendon passes iato the representative of the flexor brevis 

 digitorum pedis. The tendons of the flexor hallucis longus 

 and flexor perforans unite into a common tendon, which 



subdivides into slips for the digits. 



, 3.3 2 1 



The dental formula of the Dog is i. — - c. — -p.m. til 



... . *'* 



m. ~=42. The two upper inner incisors, on each side, have 



distinctly trilobed crowns — the lateral cusps of the crown 

 arising from outgrowths of the cinguliim at its base. The 



