MESOZOIC TIME — TRIASSIC AND JURASSIC. 



751 



valley beds, referred by E. Hitchcock to Insects, and the others (1168, 1169) 

 are regarded by him as made by Crustaceans. Nearly 30 species of these 

 delicate tracks are described by Hitchcock. 



2. Fishes. — The Fishes of the era were Ganoids and Sharks, but only 

 remains of Ganoids have been found in the American rocks ; one of them, 

 from black shales at Durham, Conn., is represented, reduced, in figure 

 1170. The largest species found is Diplurus longicaudatus Newb., about 

 three feet long. Unlike Paleozoic Ganoids, the Triassic species are not all 

 heterocercal ; many have the tails partly, or not at all, vertebrated; and 

 this is the last period in which the old Paleozoic characteristic appeared. 

 Thus, as Agassiz first observed, the progress of the ages was marked in the 



tails of the fishes. 



1170. 



1171-1172. 



Ganoid. — Catopterus gracilis ( x |). J. H. Eedfleld. 



3. Amphibians. — Portions of large crania have been found in black shale 

 in Chatham County, N.C., and in a literal ''bone-bed" at Phoenixville, Pa. 

 With the latter were teeth two inches long, of a spe- 

 cies named Eupelor durus by Cope. The figures of 

 footprints annexed, 1171, 1171 a, and 1172, 1172 a 

 (half to two thirds the natural size), are the fore and 

 hind feet of probably two Amphibians (Hitchcock). 

 The tracks were from the Connecticut valley beds. 



4. Reptiles. — The Keptiles pertain to the two 

 grand divisions of Dinosaurs and Crocodilians. 



Dinosaurs. — The Dinosaurs are mostly of large 

 size, and were so named by Owen, from Savo's, terrible, 

 and aavpo'i, lizard. They are more or less bird-like in 

 some characteristics ; these all having (1) the posterior 

 limbs the stouter, as in Pig. 1179, page 753, and some- 

 times these are the only locomotive limbs, the Reptiles 

 in that case being bipeds in walking, like birds; 

 (2) the bones of the limbs, especially the anterior, 

 often hollow ; and in some, the vertebrae of the neck 

 very cellular and light ; (3) of the pelvic bones the 

 ischium {is, Fig. 1179) is a long and often slender bone 



projecting backward, and the pubes also are long. Many herbivorous Dino- 

 saurs that were not biped in locomotion used their strong hind limbs for 



llT2a 



Amphibians.— Fig. 1171, 1171 a 

 (x 5), Amsopus Deweyanus ; 

 1172, 1172 a, A. gracilis (x |). 

 E. Hitchcock. 



