COASTS VISITED BY THE AECTIC EXPEDITION. 579 



thing of the physical geography of the Northern Hemisphere during 

 Palaeozoic times, and the causes that produced the high temperature 

 of the arctic seas during and between the Palaeozoic and Miocene 

 periods. "We now know that both American and European species 

 occur together in the rocks of King William's Island and Depot Bay 

 &c. in Bellot's Strait, and, further north still, up Smith Sound along 

 the shores of Grinnell Land and Greenland as far as 82° 43'. 



Favosites gothlandicus and Halysites catenulatus seem to be univer- 

 sally distributed through the Silurian rocks of all northern latitudes, 

 abundantly in the polar regions ; Heliolites also throve, if we may 

 judge from the size of the coralla ; and also Favistella, which, like 

 Favosites, must have flourished at moderate depths. These Acti- 

 nozoa were associated with Receptaculites, Maclurea, Orihoceras, and 

 Trilobites. Additional proof of the abundance of life is shown by the 

 formation of great deposits of limestone, both Silurian and Car- 

 boniferous, equalling in mass those in so-called warmer climates or 

 latitudes. 



The Lower Silurian series, through the Chazy, Trenton, Utica, and 

 Cincinnati groups, is represented in the polar fauna by Maclurea 

 magna, M. Logani, Ormoceras, Favistella, JSyringopora, Halysites, 

 and Trilobites. The Upper Silurian is represented by the Niagara 

 and Lower Helderberg rocks, containing Stromatopora, Heliolites, 

 Zaphrentis, Cyathophyllum, &c.,the species of which will be noticed 

 in their respective places. The Coelenterate fauna, therefore, of 

 the Silurian polar seas, judging from the character and number 

 of specimens collected by the naturalists of the Expedition, must 

 have been a large and prolific one, which, it is hoped, will some 

 day be thoroughly examined. 



Group Tabulata. 

 Genus Eavosites, Lamk. 1812. 



Favosites gothlandicus (Eougt). 



Corallum gothlanclicum, Eougt, Amcen. Acad. 1749, vol. i. p. 106, 

 t. 4. f. 27. 



Favosites gothlandica, Lamk. Hist. Nat. vol. ii. p. 206 ; M.-Edw. 

 & Haime, Mon. Brit. Sil. Corals, Pal. Soc. p. 256, t. 60. f. 1. 



Calaraopora gothlandica, Goldf. Petref. Germ. vol. i. p. 77, t. 26. 

 f. 3. 



Examples of this ubiquitous and typical coral are abundant ; in- 

 deed it is the commonest coral in the collection, occurring in every 

 locality and in fine preservation, although often too crystalline to 

 show structure. Favosites gothlandicus must have been the chief 

 and most abundant coral in the polar Silurian seas — I may say Upper 

 Silurian seas. There is scarcely a single horizon in Britain, from 

 the Caradoc to the Wenlock, in which it does not occur, its place 

 being taken in the Devonian rocks of Europe by F. Goldf ussi. These 

 two species, belonging to the massive type, abound in their respec- 



