Divisions Classes No. of Orders I. VERTEBRATA. } 1. Mammalia Nine. Four Classes. Twenty-seven Orders. } 2. Aves Six. } 3. Reptilia Four. } 4. Pisces Eight. II. MOLLUSCA. } 1. Cephalopoda One. } 2. Pteropoda One. Six Classes. Fifteen Orders. } 3. Gasteropoda Nine. } 4. Acephala Two. } 5. Brachiopoda One. } 6. Cirrhopoda One. III. ARTICULATA. } 1. Annelides Three. } 2. Crustacea Seven. Four Classes. Twenty-four Orders. } 3. Arachnida Two. } 4. Insecta Twelve. IV. RADIATA. } 1. Echinodermata Two. } 2. Entozoa Two. Five Classes. Eleven Orders. } 3. Acalephæ Two. } 4. Polypi Three. } 5. Infusoria Two. THE VERTEBRATED ANIMALS Have a backbone divided into vertebræ or joints, whence they take their name. They have also separate senses for hearing, seeing, tasting, smelling, and feeling; a distinct head, with a mouth opening by two horizontal jaws; a muscular heart, and red blood. The four classes of Vertebrata and their orders are as follow:-- I. THE MAMMALIA are all furnished with mammæ, or teats, through which they give milk to their young, which they bring forth alive. They have warm blood, which all circulates from the heart through the lungs, and returns to the heart before it passes through the body. Their skins are naked, or covered with wool or hair, and their mouths are generally furnished with teeth. There are eleven orders, which are thus distinguished:-- SECTION I.--_Unguiculated Animals, or Mammalia having Nails or Claws._ I. _Bimana_, or two-handed. This order contains only the human species. II. _Quadrumana_, or four-handed. This order contains the apes, baboons, and monkeys, and the lemurs. III. _Cheiroptera_, the bat family. IV. _Carnivora_, or beasts of prey. This order is divided into the following three tribes:-- 1. _The Insectivora_, consisting of those animals which live upon insects, as the hedgehog, the shrew, and the mole. 2. _The Carnivora proper_, consisting chiefly of the cat family, including lions, tigers, and their allies; the bear family, including the badger, the coati-mondi, the racoon, &c.; the dog family, including the wolf and the fox; the weasel family; the civet-cats; and the hyæna.