INTRODUCTION. XXV 



Sheep, &c. They have two hoofs, and two upper supplemental ones, 

 no upper incisors (except in the Camel), and flattened molars. A 

 canine is present in a few. 



The PACHYDERMATA is a more varied and artificial group than the 

 Ruminants, comprising the Elephant, Rhinoceros, Hippopotamus, 

 Pig, Horse, and Tapir. They differ much in their dentition, and 

 only agree in the negative character of not ruminating ; and perhaps 

 it would be more scientific to divide them into separate orders as 

 some have done, viz., CHCERODIA for the Hippopotamus and Pig ; 

 PROBOSCIDEA for the Elephant ; and BELLURA for the others. 



The herbivorous Cetaceans, sometimes classed with Pachydermata, 

 are generally separated as a distinct order, called SIRENIA, and are 

 distinguished from the other Diplodonts by the absence of limbs. 



The ISODONTIA, comprising the Whales, Dolphins, and Porpoises, 

 are generally called Cetacea, and have no posterior extremities, whilst 

 their anterior limbs are changed into fins. 



Such is the Classification adopted in the present work, of which the 

 accompanying synopsis may be found useful. 



A. PLACENTAL MAMMALS. 



(Foetus nourished in the uterus through a placenta.) 



I. TYPODONTIA. Teeth of all four kinds. 

 1st Group, PRIMATES. Hair of one kind only. 



Ord. Quadrwnana. With thumb on the feet. 

 ,, Cheiroptera. Winged. 



2nd Group, SECUNDATES. Hair of two kinds. 

 Ord. Carnivora. Molars trenchant mixed with tubercular ones. 

 ,, Insectivora.M.ola,Ts studded with cusps. 



II. DIPLODONTIA. Teeth generally of two kinds only, abnormal. 

 Ord. Rodentia. Front teeth long and chisel-like. 

 5 , Pachydermata. Teeth varied skin thick do not ruminate 

 Ruminantia. Upper incisors generally absent chew the cud . 

 ,, Sirenia. Want posterior extremities. 

 Edentata. Incisors absent. 



