86 . Dynamic Theory. 



Goniatites are gone, and the Ammonites and Ceratites succeed them. 

 The long race of the Trilobites is ended, and the Eurypterids, the fore- 

 runners of the Crayfish, are gone too, to be superseded by species of 

 Macrouran (long-tailed} forms, more like the lobster and schrimp of the 

 present. There are not yet any teliost fishes, but the ganoid type 

 changes in that direction, and the tails are less heterocercal and in some 

 cases quite homocercal, or equally divided, the spine ending at the tail 

 fin. The Ceratodus, Australian mudfish, is supposed to commence here. 

 See Fig. 61. Amphibians are strongly represented in the Labyrintho- 

 donts and other forms. There are also animals of the Lizzard type 

 approaching true reptiles, and others that appear to walk chiefly on 

 their hind feet. There was one, the Otozoum Moodii, that thus walked on 

 his hind feet, occasionally putting down the fore ones. The hind feet 

 were twenty inches long and the fore feet about ten. They had four 

 toes each (and probably a rudimentary thumb). Others had but three 

 toes behind and four in front. The tracks made tend to become those 

 of the toes (or fingers) instead of the wkole hand as with the_ first of the 

 Amphibians. Many three-toed tracks of this period formerly ascribed 

 to birds are now generally admitted to belong to these quasi-amphibians 

 taking on bird characteristics. The beaked Saurians, also called Anomo- 

 donts (lawless-toothed), are peculiar to this period. The most extra- 

 ordinary of this remarkable group is the Dicynodon (two-canine-toothed). 

 This was a saurian with the head and nipping horny beak of a tortoise 

 and with two long, curved, overhanging canine teeth from the upper 

 jaw. Several species have been found, in one of which (the tigriceps) 

 the head ^was 20 inches long and 18 inches wide. They have been 

 found only in the fresh water Triassic of South Africa (Karoo 

 beds). Several other genera of the same order (Anomodonts) have been 

 found in the same locality. The Oudenodon had a nipping horny beak 

 without teeth of any kind. According to Prof. Owen, this remarkable 

 order combined the characters of crocodiles, tortoises and lizzards. 



There has also been found what is supposed to be a part of a Ptero- 

 dactyl, a singular compound which becomes familiar in the Jurassic 

 period. In the upper part of the Triassic is found the first Mammal, 

 only one or two specimens consisting of the jaw bones. They are classi- 

 fied as Marsupials related to the non-placental Banded ant-eater family 

 Myrmecobius.* 



The Marsupials of the present day are all found in Australia and the 

 neighboring islands, except the Opossum group in North and South 

 America. The opossum is as large as a cat and has a long, round, 

 partly naked prehensile tail. The Myrmecobius has a bushy tail and 



*Prof. Blainville and Dr. Grant hold that these jaw bones belong to an extinct reptile 

 of higher organization than any now living, and are therefore not mammals. But the 

 current opinion seems to be the other way. JSee Cuvier, page 90. 



