TRIASSIC PERIOD. 



419 



/$h 



animals by the discovery in Triassic strata of certain tracks made by 

 a clumsy-footed animal (Fig. 619), which was at first mistaken for a 

 mammal and called Cheirotherium (hand-beast). Its true nature was 

 made known by Prof. Owen, who called it Labyrinthodont. 



The Anomodonts (lawless-toothed) 

 had jaws covered with horn, like tor- 

 toises and birds, sometimes toothless, 

 as in Oudenodon (Fig. 621), and some- 

 times with two great canines only, as 

 in Dicynodon (Fig. 620). These rep- 

 tiles were of great size. The head of 

 the Dicynodon tigriceps was twenty 

 inches long and eighteen inches wide. 

 The RhyncosaursYi&dL strongly-hooked, 

 horny beaks, like that of a parrot (Fig. 

 623 a). The curious reptile Spheno- 

 don, or Hatteria, of New Zealand (Fig. 

 623 b), is the nearest living ally. 



A 



Fig. 617. 



Fig. 618. 



Figs. 61' 



618.— Tkiassic ~REFTfLBS—Labi/nnthodonts: 617. Tooth of Labyrinthodon, natural size. 

 618. Section of same enlarged, showing structure. 



The Theriodonts (beast-toothed) are so called on account of the 

 resemblance of their teeth to those of the lowest and earliest mammals. 

 The following are the main points of resemblance : 1. The teeth are 

 in three sets, viz., incisors, canines, and molars. 2. The canines are 

 much larger than the others, and separated from them by a wide space 

 (diastema). 3. The molars (jaw-teeth) are in many cases not conical, 

 like reptilian teeth, but have commenced to develop cusps (Fig. 624) 

 like those of mammals, especially the earliest Mesozoic mammals. 

 (Compare this figure with Fig. 711, p. 449.) The canines of some of 

 these Theriodonts have been found five and six inches long. A large 



