400 THE ANATOMI OF VERTEBRATED ANIMALS. 



The calcaneal process is flattened from side to side, and lias a 

 pulley-like excavation upon its posterior extremity. The 

 tibial facet of the astragalus is inclined slightly inward, as 

 well as upward, and its outer edge is raised. The distal di- 

 vision of the tarsus, consisting of the cuboid and navicular, 

 with the cuneiform bones, is capable of a considerable amount 

 of rotatory motion upon the astragalus and the calcaneum. 

 The ento-cuneiform bone is large, and has a transversely-con- 

 vex articular surface for the metatarsal of the hallux. Conse- 

 quently the latter (which is short, reaching to only about the 

 middle of the proximal phalanx of the second digit) is capable 

 of free motion in abduction and adduction. 



In the Cynomorplia^ and even in the so-called " tailless " 

 genus, Iriuus, proper caudal muscles are present. In the limbs 

 there is a levator clavlcidm which passes from the transverse 

 process of the atlas to the acromion ; a dorso-epitrochlearis^ 

 consisting of a muscular bundle detached from the latlssimus 

 dorsi near its insertion, and passing to the distal and inner 

 end of the humerus, or even farther down ; a scansorius^ from 

 the ventral edge of the ilium to the great trochanter, which 

 sometimes becomes confounded with the glutCBUS tninimus j a 

 special abductor ossis metacarpi quinti / and a peronceus 

 qui?iti digitiy arising from the fibula, between the peronmxis 

 longus and brevis, j^assing behind the external malleolus, and 

 sendino- its tendon to the extensor sheath of the fifth dig-it. 



The extensor primi internodii pollicis and the peronmus 

 tertius are absent in this, as in the preceding group. 



The biceps fernoris usually possesses only an ischial head, 

 and the soleus arises only from the fibula. The flexor brevis 

 digitorum arises partly from the tendon of the 2^^^^daris^ 

 where this passes over the joulley on the posterior surface of 

 the calcaneal process to become continuous with the plantar 

 fascia, and partly from the tendons of the long flexor. The 

 transversus pedis is usually fully developed, but has only two 

 heads of origin from the distal ends of the second and third 

 metatarsals. The inter ossei pedis are just visible on the dor- 

 sal aspect of the foot, but none are, properly speaking, dorsal. 

 None of them are penniform muscles arising from adjacent 

 sides of the metatarsal bones ; but they are attached, in pairs, 

 to the plantar and lateral aspects of the metatarsal bones of 

 the digits to which they appertain. They are inserted into 

 the sesamoid bones, of which each digit has two, and into the 

 bases of the proximal phalanges, and give off no distinct ten- 

 dons to the extensor sheaths. Additional muscles may arise 



