COMPENDIUM OF GENERIC DISTINCTIONS. 



EXPLANATION OF SIGNS AND TERMS. 



TEETH. 



INCISORS. These are the teeth which are placed 

 in the front of the jaw. They are inserted in the 

 premaxillary bones, and in the corresponding por- 

 tion of the lower jaw. They are termed "incisors," 

 or cutting teeth, from the Latin word incidere, which 

 signifies " to cut," even though their edges should 

 not be formed for cutting. 



CANINES. These teeth are situated next to the 

 incisors, and are inserted at or close to the suture of 

 the premaxillary bones in the upper jaw. In the 

 lower jaw, the canines are set opposite to those of 

 the upper jaw, and when the mouth is closed pass 

 in front of the crown of the upper canines. They 

 are called " canines," from the Latin word canis, a 

 dog, because they are largely developed in the dogs. 



PR^MOLARS. These teeth are situated behind 

 the canines, and next to the true molars. The word 

 " molar " is derived from the Latin mo/a, a mill, be- 

 cause these teeth serve to grnd the food. Popu- 

 larly they are called "grinders." In human sub- 

 jects the praemolars are sometimes termed the 

 "bicuspids," on account of the double cusp on their 

 surfaces. 



MOLARS. These teeth are permanent, and are 

 situated behind all the others. They are often not 

 developed until comparatively late in life. 



THE DENTAL FORMULA is a concise mode of 

 describing the number and positions of the various 

 teeth, and is easily comprehended. The accom- 

 panying formula is that of Man : 



2 2 i i 2 2 3 3 

 I. , c. , P. , M. = 32. 



22 I I 22 33 



In these formulas the upper figures refer to the 

 teeth of the upper jaw, and the lower line to those 

 of the lower jaw, while the short hyphen serves 

 to separate the right from .the left side. In man, 

 therefore, there are two incisor teeth on each side 

 of the upper jaw, and the same in the under jaw; 

 one canine on each side of the upper jaw, and the 

 same in the lower jaw ; two praemolars on each side 

 of the upper jaw, and the same in the lower; three 

 molars on each side of the upper jaw, and the same 

 in the lower ; in all, thirty-two in number. The den- 

 tition is always presumed to be that of the adult 

 animal. 



CLASS I. MAMMALIA. 



ANIMALS possessed of vertebrae ; breathing at- 

 mospheric air by lungs ; heart wth two auricles and 

 two ventricles ; blood warm and red ; producing 

 living young ; nurturing them by milk, which is se- 

 creted in the " mammary glands ; " skin covered 

 with hair, spines or scales. 



. BIMANA. 



Hands and feet five-fingered, the nails all flat and 

 broad. All the teeth even and close to each other, 

 the molars equally enamelled. In this order there 

 is but one species, namely Man, Homo sapiens. 



2 2 i i 

 Teeth. I. , C. , 



2 2 



P. 



Ttr 3 ~ 3 



M. . = 32. 



22 I I 22 33 



Order, QUADRtfMANA. 

 Hinder feet five-toed, the thumb opposable to the 

 others ; fore-feet sometimes four-fingered, the thumb 

 being absent. Molar-teeth equally enamelled ; with 

 one exception, the Cheiromys, they possess incisor, 

 canine, praemolar, and molar teeth. Skin covered 



with hair, with the exception of the palms of the 

 hand, the face, and the callosities of the hinder 

 quarters. Mammae placed on the breast. 



Family. SlMlAD>E. 



Teeth. Molars, -, the false molars being tuber- 

 culato. 5 



Nails rather flat or slightly rounded, and not point- 

 ed like claws. Fore-feet almost always five-toed. 

 Thumb opposable. Tail never prehensile. 



Genus. Troglodytes. 



Teeth. I. 



2 2 



I I 



2 2 



C. 



p. 



M. 



2 -2 



I I 



2 2 



33 



33' 



= 32. 



Canines slightly elongated, and placed close to 

 the incisors. 



Head. Muzzle rather short Cheek-pouches 

 none Ears large and projecting. 



Tail. None. 



Habitat. Western Africa. 



