118 21ie Carboniferous Fauna of America 



proves that the appearance of this class of animals, more 

 ancient than has been believed until now, was contempora- 

 neous on the two continents. 



The trilobites follow a similar order of decrease, and are 

 reduced in America as in Europe, to small species of the 

 genus Phillipsia. The Goniatites offer also for the first time 

 the new type, where the dorsal lobe, instead of being simple, 

 is divided by a small medial saddle. 



The distribution of the Productus offers another remark- 

 able coincidence. Unknown in America in the Silurian sys- 

 tem, appearing under one or two small forms in the Devonian 

 epoch, the species assume in the carboniferous rocks a de- 

 velopment altogether in harmony with the facts observed in 

 Europe. The Spirifers of this epoch present also in America 

 the character of having the plications often dichotomous, 

 which M. d'Ai'chiac has already indicated in Europe,* and 

 by which they are distinguished from those of the Devonian 

 epoch, which have them always simple. t 



As to the Terebratulte, we will mention the interesting fact 

 of the simultaneous disappearance of two species, the T. re- 

 ticularis and T. aspera, which, during the Devonian and 

 upper Silurian epochs, were spread with great profusion from 

 the Altai and Ural to the Missouri. We will cite also, as 

 simultaneous phenomena upon the two continents, the appear- 

 ance of those Crinoids forming a passage to the Echinoderms, 

 such as the Faloeechimts or Melonites, the extinction of those 

 great corals, sucli as the Favosites Gothlandica, Porites inter- 

 stincta, kc, and their replacement by the Chcetetes awdi Lith- 

 ostrotion, nearly identical in Europe and America. The ana- 

 logy between the two continents continues open to the Fo- 

 raminifera and the plants. We have seen, indeed, that the 



* Memoir on the Palaeoz. For. (Trans. Geol., vol. v., p. 319). See also Geo- 

 logy of Russia in Europe, vol. ii., p. 126. Von Ruch, in his interesting Me- 

 moir which he has published upon Cherry Island (Baren Jnsel) has insisted, with 

 reason, ou the importance of this character, which might be thought insignifi- 

 cant. 



t It is also only at the Devonian epoch that we find the Spirifers in which 

 the back is divided by a slight furrow, as in S. mucronatus and Bourhoidi. 



