312 APPENDIX. 



range.* P. Humboldtii is found in Russia and South 

 America. Our P. mammatus (?) is probably distinct from 

 the Russian species, but it is at all events the same 

 as one in Captain Belcher's collection f. 



The size of the fossils, both of the shells and Bryozoa, 

 is remarkable, and, taken in conjunction with the pre- 

 sence 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. 



X Quarterly Journal of the Geological Society. 



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