18 



SUBKINGDOM VBETEBRATA. 



single species of the domestic animals. We therefore agree 

 with Dr. Prichard " that no other differences occur than 

 may fairly be attributed to the differences of external cir- 

 cumstances ; and hence it may safely be concluded that the 

 different races are all members of the same family, and the 

 offspring of one common stock." 



Dental Formula. — As the teeth present important char- 

 acteristics for classifying the mammals, zoologists designate 

 ihe number by a formula which, as applied to man, reads 



.2-2 1-1 2-3 3-3 ^„ ^,. 



il,^,.. ^^^^, c^__^^, pm.-~^^,m^—^ = i2. This 



signifies that there are eight incisors, two on each side of 

 each jaw ; four canine teeth back of the incisors ; eight pre- 

 molars (bicuspids) back of the canine; and twelve molars 

 back of the premolars. 



Fig. It. 



ORDER QUADRUMANA. 



General Characteristics.— The peculiar feature of 

 Monkeys is the power of opposing the great toe to the other 



toes, making the hind feet be- 

 come hands snd the animal 

 quadrumanous or four-handed. 

 They are further distinguished 

 from man by the spinal open- 

 ing in the cranium being in 

 the posterior third of the base ; 

 by the "single curve of the ver- 

 tebral column; the shortness 

 of the thumb, which does not 

 reach the base of the index 

 finger; the long and narrow 

 pelvis ; the impossibility of 

 placing the foot at right angles with the leg, the sole resting 

 on the ground ; the relative length of the arms, which reach 

 at least to the knee, and in some species to the ankle ; the 

 greater prominence of the canine teeth, etc. 



a, Monkey's hand midfoot. 



b, Human hand and foot. 



