HEEE — CAEB0NIFEE0U3 FLORA OP BEAK I3LAKD. 165 



stinguislied from tlieni with great difficulty. For example, the 

 most abundant fern of St. John's, PecojJteris discrepans, Daws., is 

 hardly to be distinguished from Pecopteris Joncliitica, a species 

 which, both in America and in Europe, is abundant in the Carboni- 

 ferous. In the same manner, Cordaites Rohhii, Daws., is so near 

 C. horassifolius, Sternb., sj),, that, according to Dawson, it may 

 often be mistaken for it ; and Asterophyllites parvulus, Daws., is 

 scarcely distinguishable from A. delicattdus, Sternb. (Bechera). 

 Therefore the St.-John's flora has in fact the character of the Lower 

 Carboniferous formation, and the only question is whether it does not 

 approach more nearly to the Millstone- grit flora (with which it has 

 five species in common) than to tlie Ursa stage. Bj this also it be- 

 comes doubtful whether the Catskill and Chemung groups do not 

 belong rather to the Ursa stage than to the Upper Devonian. 



In the arctic zone, besides the Bear-Island flora, we may regard 

 the sandstones of Parry Island as belonging to the Ursa stage. In 

 Melville Island also the sandstone lies under the Mountain Limestone; 

 and the Knorria acicidaris, which is found in it, serves as a point of 

 contact with the Bear-Island flora, and shows that these plants of 

 South Ireland and the Yosges reached as far as 76° JST. lat. 



If we add the plants of St. John, Kiltorkan, the Vosges, the south 

 Black Forest, and the Yerneuilii-shales to those of Bear Island, they 

 yield to the Ursa stage a flora of seventy-seven known species, of 

 which three are common to the Devonian and seven to the Middle 

 Carboniferous. Of the former, however, one, and of the latter 

 three species are doubtful, either in their determination or in 

 their geological position. With the Upper Carboniferous (the Per- 

 mian) the Ursa stage has not a single well-determined spiecies in 

 common ; with the Mountain Limestone it has thirteen species, and 

 with the MiUstone-grit twelve ; and with the two united, eighteen 

 species. Among these are the most frequent species, such as form 

 the true typical plants of the Lower Carboniferous, namely Ca- 

 Jamites radiatus, Lepidodendron Velthehnianum, Knorria imbricata, 

 Cardiopteris frondosa, and C. polymorplia. One of the most charac- 

 teristic genera of the Ursa stage is Cyclostigma. 



The flora of the Mountain Limestone and its equivalents appears 

 to be less rich than that of the Ursa stage ; the culmiferous beds, on 

 the contrary, have yielded a large number of plants, as have also the 

 Greywacke andPosicZononi2/<^(-shales of the Harz, Silesia, and Moravia. 

 If we compare the plants from these difl^erent places, we find in each 

 a number of peculiar forms, which probably arises from the flora being, 

 as yet, so little known to us ; but wc find also many sj)ecies in common, 

 which throughout are the most abundant and consequently the most 

 important of the localities. These are chiefly the typical plants men- 

 tioned above. The Millstone-grit flora, when compared with that of 

 tho Ursa stage, is remarkable for the increase in the number of spe- 

 cies common to the Coal-measures ; among these are species which 

 have a wide range through the formation, such as Neuropteris Loshii 

 and Ccdamites SacJcoivii. The newer Greywacke, also, which forms a 

 passage to the Coal-measures, is distinguished from them by the 



vol,. XXVIir.— PAET I. N 



