282 APPENDIX. 



curs in similar whitish limestone. These may possibly have 

 all come from the locality whence M. Robert's original speci- 

 mens were found ; but it would appear that they are not by 

 any means the prevailing fossils of the island. 



The general aspect of the fossils is unquestionably carbon- 

 iferous, and some of the species have a wide diffusion. Pro- 

 ductus costatus ranges from India to the Mississippi, and P. 

 semireticulatus (which I think is only a variety of the same 

 species) has even a wider range.* P. Humboldtii is found in 

 Russia and South America. Our P. mammatus f is probably 

 distinct from the Russian species, but it is, at all events, the 

 same as one in Captain Belcher's collection.! 



The size of the fossils, both of the shells and Bryozoa, is re- 

 markable, and, taken in conjunction with the presence of large 

 land-plants in the coal, would seem to indicate a great decrease 

 of temperature in the Arctic region since the Carboniferous 

 period. The shells are larger, too, than the corresponding 

 species in our own mountain limestone. J 



* To Australia (M'Coy). 



t It is closely and finely striate, and has spines along the hinge-line only. 



% Quarterly Journal of the Geological Society. 



THE END. 



