378 ANATOMY OF VERTEBRATES. 



Eats, Marmots. In many Rodents the angle is extended out- 

 ward and subsides, advancing, as a ridge upon tlie outer side, of 

 the horizontal ramus, as in fig. 242 : in Ctenomys the breadth of 

 the mandible exceeds the lengtli. Most Cavies show, also, the 

 external ridge noted in the Capybara's jaw, below the molar 

 series. The upper jaw is similarly modified in relation to the 

 masseter, e.g., in those Kodents which have the fore part of the 

 muscle passing through the wide antorbital vacuity, v, to its peri- 

 pheral ridges. 



C. Bones of the Limbs. — In this extensive and ubiquitous order, 

 which includes three-fourths of the known species of Mammals, 

 some have limbs giving power in running, some in swimming, 

 some in burrowing, some in leaping, some in climbing, and a few 

 show modifications in relation to parachute-like expansions of 

 integument for a kind of flight. 



In the Hare, fig. 229, the scapula is long and narrow, traversed 

 externally by a spine extending into an acromion at an unusual 

 distance beyond the glenoid ca\dty, and there developing a retro- 

 verted process ; the coracoid is compressed and introverted. The 

 clavicular ossicles are freely suspended, allowing full swing to the 

 fore-limb. The humerus, long, slender, and sigmoid, has a large 

 intercondyloid vacuity. The radius and ulna are in close contact ; 

 the latter is grooved for the reception of the radius. Their gingly- 

 moid joint mth tlie humerus restricts the movements to one plane. 

 The carpus has the ^ os intermedium,' fig. 191, s'. There are five 

 digits, the innermost very short, though with the normal number 

 of phalanges. The fore limbs are relatively shorter and stronger 

 in the burrowing Rabbits ; the ungual phalanges are less com- 

 pressed, and aiford a closer attachment of the broader claws by 

 being cleft on the upper surface. In all Leporidce the ilia are 

 long and subprismatic where they articulate mth the sacrum, the 

 joint being limited to the first vertebra, fig. 245, a, b. They 

 extend in advance of this on each side the last lumbar, ib. d, ex- 

 ])anding into a crista, c, which is rough and slightly everted : the 

 ilia form with the lumbar series an angle of 165°, fig. 229. The 

 ischia have a process, fig. 244, e, above the terminal tuberosities : 

 the pubic bones are long and slender, meeting at a long symphysis 

 produced into a ridge,/: there is a ^ pectineal ' process, d, near the 

 acetabular end of the pubis. The iliopubic angle is about 120°. 



The femur has a third trochanter near the base of the great 

 one. The medullary artery pierces the inner side of the proximal 

 third of the bone, and the canal extends downward. The fibula 

 is anchylosed along its distal half to the tibia : its proximal end 



