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 portion of the lower jaw. They are termed 

 11 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 crowns of the upper canines. They arc called 

 "canines," from the Latin word canis, a dog, because they are 

 largely developed in the dogs. 



Premolars. — These teeth are situated behind the canines, and 

 next to the true molars. The word " molar " is derived from the 

 Latin mola, a mill, because these teeth serve to grind the food. 

 Popularly they are called "grinders." In human subjects the 

 praemolaia 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 com- 

 prehended. The accompanying formula is that of Man :— 



I, 



a-a 



3-2' 



c. 



1-1 



1-1' 



p. 



2 2' 



M . ±± = 33. 

 3—3 



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 premolars 

 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 dentition is always 

 presumed to be that of the adult animal. 



CLASS I. — MAMMALIA. 



Animals possessed of vertebrae ; breathing atmospheric air by 

 lungs ; heart with two auricles and two ventricles ; blood warm 

 and red ; producing living young ; nurturing them by milk, which 

 is secreted in the " mammary glands ; " skin covered with hair, 

 spines or scales. 



Order.— BiMANA. 



Hands and feet five-fingered, the nails all flat and broad. All 

 the teeth even and close to each other, the molars equally enam- 

 elled. In this order there is but one species, namely, Man,— 

 Homo sapiens. 



2—2 „ 1—1 „ 3—3 „ 3—3 



Teeth.— I. 



2—3 



1—1' 



P. 



M. 



3—3 



= 33. 



Order. — QUADRtJMANA. 



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. Mamma? placed on the 

 breast. 



Family. — Simiad^:. 

 5 

 Teeth.— Molars, '-, the false molars being tuberculate. 



Nails 



rather flat or slightly rounded, and not pointed like claws. 

 Fore-feet almost always five-toed. Thumb opposable. Tail 

 never prehensile. 



641 



Genus. — T rogl odytes. 



Teeth.— I 



2—2 

 2—2' 



C. 



1—1 

 1-1' 



3—3 



M 



3—3 



2—3 3—3 



= 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. 



Genus. — Simia. 



Teeth. — Canines much exceeding the others in length, and 

 overlapping each other when the mouth is closed. — Two central 

 incisors extremely broad. 



Head. — Muzzle projecting very considerably — Ears small, and 

 placed close to the head — Cheek-pouches none. 



Limb-. — Arms extremely long, the fingers resting on the ground 

 when the animal stands erect. 



Habitat. — Borneo and Sumatra. 



Genus. — Siamanga. 



Head small, and muzzle short — Cheek-pouches none. 



Throat furnished with a large air-pouch. 



Limbs. — Arms extremely long — First and second fingers of the 

 hands united as far as the middle of the second joint — Slight 

 callosities on hinder quarters. 



Habitat. — Sumatra. 



