GENERAL OBSERVATIONS. 303 



time nearly an extinct tribe. With a rare exception, the vertebrate 

 character of the tail does not recur after the Palaeozoic. 



The further history of the type of Fishes is a subject of special 

 interest, as will appear in the sequel. 



Besides land-plants and fishes, reptiles are supposed to date from 

 the last epoch of the Devonian- — though the evidence is not beyond 

 suspicion, as stated on p. 299. If correct, the beds may still be 

 synchronous with those called Lower Carboniferous in Pennsyl- 

 vania, in wliich similar tracks have been observed ; and in this 

 case the discrepancy between the facts thus far ascertained on the 

 two continents is slight. Eemarks on the Eeptilian remains are 

 therefore deferred to a following page, under the Carboniferous. 



The progress of life during the Devonian is further seen in — 

 (a.) The introduction of many new genera under old tribes ; for 

 example, Productus among Brachiopods, which began in America 

 in the Corniferous period, and had its maximum display, and also 

 its extinction, in the Carboniferous age ; Goniatites among Cephalo- 

 pods, which had its earliest American species in the Hamilton 

 period, and became extinct at the same time with Productus, — ■ 

 a genus of interest, as it is the first of a family (that of Ammon- 

 ites) which had a wonderful extension under other genera in the 

 Eeptilian age, and became extinct to its very last species at the 

 close of that age ; Nucleocrinus (fig. 452), the earliest (after a single 

 Lower Silurian genus) of the Pentremites, another of the eminently 

 Carboniferous types ; the ellipsoidal form of Xucleocrinus is changed 

 to the pentagonal of Pentremites (fig. 531) with the first of the 

 Subcarboniferous species, or even before, in the Upper Devonian. 



(b.) The complete or approximate extinction of tribes: as that 

 of the Cystids, which ended with the Oriskany period in America 

 and the epoch of the Eifel limestone in Europe ; that of Favistella, 

 Heliolites, and other genera of Corals and Crinoids ; that of Atrypa, 

 Calceola, Stringocephalus, and other genera of Brachiopods ; that of 

 the Chain-coral, or Halysites, which does not appear above the Upper 

 Silurian in America, but is found in the Eifel limestone in Europe : 

 that of Trilobites, which, after there had been, under a succession of 

 genera, over 600 species, came nearly to its end in the Devonian, 

 the old genera being all extinct, and only three new ones appearing 

 in the Carboniferous, to close off this prominent Palaeozoic type ; 

 the Orthoceras family, species of which are comparatively rare fossils 

 after the Devonian age. 



(c.) In the historical changes in tribes or genera : for example, 

 the Sphifers, which began in narrow species in the Upper Silurian, 

 become broad-winged and very numerous in the Devonian, and 



