SKELETON OF KODENTIA. 383 



hand is pentadactyle, and the whole anterior extremity much 

 shorter than the posterior one. The ihac bones extend upward 

 considerably above their junction with the anterior sacral verte- 

 brie, and curve outward. The tuberosities of the ischia are un- 

 usually developed. The obturator vacuities are very extensive, 

 the size of the pelvis according with that of the hinder extre- 

 mities. The great trochanter is of unusual length, is expanded 

 and slightly bent at its extremity. The fossa upon the neck of 

 the femur is unusually deep ; there is no third trochanter. The 

 medullary artery enters on the inner side of the base of the 

 small trochanter. The slender fibula coalesces with the lower 

 third of the tibia, but both its extremities are free, and the lower 

 one is detached, as in the Chevrotain, from the rest of the bone. 

 The calcaneum, astragalus, and cuboid are all remarkable for 

 their length : the scaphoid sends a long and thick process do^^Ti- 

 ward and forward to beneath the middle cuneiform and the base 

 of the inner metatarsal. There are four distinct metatarsals and 

 four toes. An oblong ossicle, attached to the inner side of the 

 base of the inner metatarsal, may be a rudiment of the metatarsal 

 of the hallux. 



In the Smaller Jumping Mouse {Dipus Sagitta), fig. 232, may 

 be noticed the large size of the ischium, as compared with the 

 ilium, and the coalescence of the metatarsals of the three middle 

 toes into one bone, m, as in Birds. Both hallux and little toe are 

 wanting. The lower half of the slender fibula is anchylosed to 

 the tibia. 



The climbing Squirrels {Sciuridce) have four digits on the fore 

 foot, and five digits on the hind foot, conversely to the Helamys. 

 All possess complete collar-bones. In Sciurus maximus the 

 acromion is bent almost at right angles with the spine of the 

 scapula, and it terminates in three prominences : the coracoid is 

 unusually long. The humerus is perforate above the inner 

 condyle, but not between the condyles. In the femur the small 

 trochanter is unusually prominent : there is also a trochanterian 

 ridge below the base of the great trochanter. In the Grey 

 Squirrel {Sc. cinereus) the scapula is remarkable for the num- 

 ber and strength of the intermuscular cristfe : of these, that 

 which is commonly called the ' spine ' is the largest, its breadth 

 being equal to that of the infraspinal fossa : this fossa is bounded 

 by a second ridge, formed anteriorly by the outwardly bent 

 lower costa, but being distinct from the costa at its posterior 

 third. The two principal masses of the ' subscapulars ' muscle 

 are divided by a longitudinal crest, like the spine, rising from 



