TRIASSIC PERIOD. 



417 



iii Australian rivers (Fig. 438, p. 338), is traced back to this period. 

 Being known in a fossil state only by the curious palatal teeth (Fig. 



Fig. 605. 



Fig. 607. 



Fig. 608. 



Figs. 603-608— Lamellibkanchs (after Nicholson): 603. Daonella Lommelli. 604. Pecten Valoni- 

 ensis. 605. Myophoria lineata. 606. Cardinal Rhaeticum. 607. Avicula contorta. 608. Avicula 

 socialis. 



612), it has heretofore been classed with Placoids. The Placoids are 

 partly Cestracionts (Fig. 613), and partly Hybodonts (Fig. 614). 



. : * * 



Fig. 610.— Pemphyx Sueurii 



— Ceratites nodosus. 



Fig. 611.— Glaphroptera pterophylli (after Heer). 



Reptiles. — The reptiles of the Triassic are imperfectly known. They 

 belong mainly to four orders, viz. : 1. Labyrintliodonts ; 2. Rliyncosaurs 

 (beaked Saurians) ; 3. Anomodonts (lawless-toothed) ; and, 4. TJierio- 

 donts (beast-toothed). The last two are sometimes united in one order 

 — Theromorpha. The Labyrinthodonts are found also in the Carbon- 

 iferous and Permian ; but the other three orders are characteristic of 

 the Triassic and Permian, and therefore of peculiar interest. 

 27 



