422 MESOZOIC TIME — REPTILIAN AGE. 



Vertebrates has from this earliest period of the Mesozoic all its 

 grander subdivisions or classes represented. 



The Fishes are all Ganoids (fig. 638), like the Palaeozoic, but they 



Carnivores ; the Rodents represent the Herbivores ; and the Edentates, or Sloth 

 tribe, the 31utilates. The Sloth tribe contains some large animals, but they 

 have overgrown bodies, too bulky to be wielded well by the small life-system 

 within. A system of structure fitted for active movement would have been 

 thrown away upon them. 



The true classification of Mammals is, hence, as follows : — 



I. Archonts — Man (alone). 



II. Megasthenes. 



1. Quadrumana, or Monkeys. — The members (or at least the posterior) 



furnished with hands, — that is, having a thumb opposable to the 

 fingers for grasping; incisors two on each jaw; clavicles perfect; 

 mammae pectoral. 



They include (1.) The Strepsirrhines, found in Madagascar, and 

 diverging thence to Africa and the East Indies, having curved 

 or twisted terminal nostrils, and the second digit of the hind 

 limb a claw. 



(2.) The Platyrrhines, peculiar to South America, having the nostrils 

 subterminal and wide apart, the thumb of the fore hand not 

 opposable, or wanting, and the tail in most prehensile. 



(3.) The Catarrhines, confined to Africa and Asia, excepting one at 

 Gibraltar, having the nostrils oblique and approximated below, 

 and opening above and behind the muzzle; the thumb of the 

 fore hand opposable. 



These are the higher species, and among them the highest group is 

 tail-less (the Orang and Chimpanzee). 



2. Carnivores (Flesh-eaters, Beasts of prey). — Feet with claws (ungui- 



culate) and the lower surface having the special sense of touch. The 

 incisors three either side in each jaw (except in the Seals), and the 

 canines one; canines longer than the other teeth. Molars trenchant 

 or tuberculate, according as the food is more or less completely of 

 flesh ; clavicle rudimental or wanting. 



(1.) Digitigrades. — Walking on the toes, without touching the heel 



to the ground, as the Lion, Cat, Dog, Weasel. 

 (2.) Plantigrades. — The palm of the hind feet touching the ground 



in walking, as the Bear, Raccoon, Badger. 

 (3.) Pinnigrades. — Moving by means of fin-like paddles, as the 

 Seal, Walrus. 



3. Ungulates, or Herbivores (Plant-eaters). — Feet hoofed, unfit for 



grasping, and of low tactile sense; the limbs restricted in use to sup- 

 port and locomotion. Molars with broad summits, for grinding. 

 No clavicles. 



The number of toes is either even or odd, — that is, either two or 



four, or one, three, or five ; and an important distinction is based 



upon this by Owen : — 



(1.) Artiodactyls, or even-toed. — Dorso-lumbar vertebrae nineteen. 



Horns, if any, in pairs. Include (1) the Ruminants, or animals 



