314 ANNUAL OF SCIENTIFIC DISCOVERY. 



ON THE DISCOVERY OF THE ICHTHYOSAURUS WITHIN THE 



ARCTIC CIRCLE. 



Among several interesting fossils brought home by the recent Arctic ex- 

 pedition, tinder Sir Edward Belcher, were some fossil remains of the Ichthyo- 

 saurus. The position where the remains were found is on the summit of 

 Exmouth Island, about 700 feet above the level of the sea. The upper 

 stratum is limestone, containing numerous fossils, and is about thirty feet in 

 thickness. The inferior stratum is entirely of red sandstone, of a deep red 

 color, which gave to the island, in the first instance, the name of Red Island. 



CONNECTION OF FOSSIL FOOT-PRINTS WITH THE THEORY OF 



PROGRESSIVE DEVELOPMENT. 



* 



At a recent meeting of the Boston Society of Natural History, Professor H. 

 D. Rogers exhibited a number of fossil impressions occurring in the red shale, 

 or carboniferous red sandstone, next underlying the anthracite coal measures 

 of Pennsylvania. A portion of them are identical with specimens found some 

 years ago, by Isaac Lea, Esq., of Philadelphia, in the same geological horizon, 

 and by him attributed to Reptilians; others are from a horizon 1,300 feet 

 lower. These specimens also present a series of impressions, not observed by 

 Mr. Lea in his specimens, consisting of the right and left feet, and apparently 

 the fore and hind feet of a small species. Professor Rogers had not yet formed 

 definite conclusions as to their nature, but they are obviously Reptilian. 

 They occur invariably upon surfaces which appear to have been slimy and 

 exposed to the air : some show the spots which are attributed to rain-drops ; 

 others, trickling water marks and wave marks. The slimy surface is attrib- 

 uted by Professor Rogers to the finest clayey deposit from the ocean, at dif- 

 ferent intervals, giving the rock the tendency to scale off in thin layers. The 

 thickness of the carboniferous red sandstone is estimated by Professor Rogers 

 at 3,000 feet; some of these specimens came from a depth of 2,000 feet in 

 that formation, and appear to be the oldest vestiges of reptilian creatures yet 

 found in the palaeozoic rocks of America. The position of the footprints dis- 

 covered by Mr. Lea is 1,000 or 1,500 feet above the base of the conglomerate, 

 or first member of the coal measures, while these described by Professor 

 Rogers extend, as has just been stated, some 2,000 feet below that geological 

 horizon. 



Longitudinal markings, looking like trails, probably of mollusca, are often 

 found in these rocks, and were exhibited by Professor Rogers. The most 

 common of these impressions is about half an inch in breadth, and consists of 

 three separate lines of corrugations, the central band having the corrugations 

 exceedingly minute. Toward one margin of the trail there is invariably a 

 narrow, sharp groove, two or three inches in length, which runs out by a 

 gentle curve toward the edge of the trail, and another commencing within the 

 margin, aud terminating likewise by a slight inflection in advance of the first. 



