70 Frof. A. E. NordensUold — Geology of Spitzhergen. 



A couple of others, Atliyris Boissyi, Leveille, and CamaropJioria 

 crumena, Mart., were also considered to occur only in Permian strata 

 until Davidson by liis accurate researches showed, in his monographs 

 on the Permian and Carboniferous Brachiopoda of England, that they 

 were common to both formations. He considers (according to 

 Kamsay, Anniv. Addr. of the Pres. GeoL Soc. of London, 1863, 

 page 22) that the half of the Permian Brachiopoda were surviving 

 Mountain Limestone species. We must suppose, for example, that 

 Productus cancrini also occurs in the Carboniferous formation in 

 Kussia and England, and thus is one of the common species ; but 

 there still remains, besides StropJialosia and Camaro'phoria, a type so 

 distinct as Productus horridus, which occurs in Spitzhergen as two 

 different races or varieties, of which one attains a giant-like size, 

 viz. 86 millimetres in height and 67 mm. in breadth, while the 

 largest Permian specimens are only 43 mm. high and 42 mm. broad. 

 As the preponderating number of fossils are such as characterize the 

 Mountain Limestone of the Carboniferous formation, we must 

 suppose that types which in the rest of Europe made their first 

 appearance after the formation of the great Coal-measures here lived 

 contemporaneously with species which were anterior to the de- 

 position of these beds in other countries. We may accordingly 

 suppose that the Permian species after the lapse of a lengthened 

 period migrated to the rest from another sea, in which new circum- 

 stances had arisen. 



What besides gives the Mountain Limeston-e fauna of Spitzhergen, 

 so to speak, so Permian a character — granting that it is only negatively 

 — is the complete absence of any representative of the genus OrtMs, 

 which appeared during the Coal Period, and numbered fifteen species, 

 extremely rich in individuals and widely spread, while during the 

 Permian age there was not a single one to be seen. 



The Permian is not the only formation with which the Moun- 

 tain Limestone on Spitzhergen has species in common. BhyncJionella 

 jpleurodon, Sowerby, increases the niunber of the species, which, like 

 Stropliomena rhomb oidalis and various Polyzoa and Corals, survived 

 from the earlier Silurian age to the Carboniferous formation. Among 

 the numerous varieties of the last-named Brachiopod is that one 

 Davidson delineated in his monograph on the Mountain Limestone 

 Brachiopoda of England, plate xxiii, fig. 12, in all respects com- 

 pletely corresponding with that variety of the Silurian BTiynclionella 

 Wilsoni, Sowerby, which he delineated in his Silurian monograph, 

 plate xxiii. fig. 10. 



If we accept a number of not less than twenty varieties of species 

 of Brachiopoda, which are distributed over nearly all the countries 

 where the Mountain Limestone is found, there remain some which 

 closely connect the Mountain Limestone of Spitzhergen with that of 

 Russia. These are Spirifer incrassatus, Spirifer hisulcatus, var. Sa- 

 rana, Terehratida fusiformis, Productus Humboldti, CJionetes variolaris. 



The species most characteristic of the Mountain Limestone of 

 Spitzhergen are Productus cancrini, Prod. Weyprecliti, and Prod, 

 horridus, which occur in great abundance at most of the localities. 



