346 E. Billmgs on the occurrence of 



concretions. In some localities such as at Reval, Poddis, Chud- 

 leigh, and Narwa, it becomes a magnesian limestone. 



In lithological characters it therefore resembles the Calciferous 

 sandrock, which, in the western or undisturbed portion of Canada, 

 abounds in magnesian strata ; and in the eastern, where it is ex- 

 panded to a great thickness by the addition of slates and sand- 

 stones holds much chlorite where partially metamorphosed. The fos- 

 sils cited by Schmidt are Orthis callifframma, 0. extensa, 0. parva, 

 0. ohtusa, Orthisina j)lana, Rhynconella nucella, and fragments 

 of trilobites of the genera Illsenus and Asaphus. In the lime- 

 stones of Point Levi and Phillipsburgh we have three species 

 scarcely distinguishable from 0. parva, 0. ohtusa, and 0. plana. 

 So far as we can judge from external characters H. nucella is a 

 Camerella, differing from C. calcifera in having the beaks closely 

 incurved. The aspect of the Calciferous Brachiopods, so far as 

 they are known, is more like that of the same group of fossils in 

 the Chloritic limestone of Russia than that of any other formation. 

 The Thonschiefer or clay slate lying next below the Chloritic 

 limestone is for us a most interesting formation, as it proves that 

 in Kussia there is (in or near the horizon of the Calciferous Sand- 

 rock) a Zone of Graptolites. It is described as a bituminous 

 clay-slate, or alum-slate, with no fossils except traces of Obolus 

 and an abundance of graptolites. Of these latter Schmidt iden- 

 tifies the following : 



Graptolithus Sedgewickii. (Portlock.) 

 G, serratulus. (Hall.) 



Dictyonema flahelliformis. (Eichwald.) 

 It is not easy to identify species of graptolites, but with respect 

 to the above it should be borne in mind that G. serratulus is a 

 remarkable form consisting of two stipes diverging at an obtuse 

 angle ; and so Schmidt describes the Russian specimens. In New 

 York it occurs at Norman's kill, associated with another species of 

 the same type G. divaricatus. (Hall.) Schmidt may be wrong as 

 to the perfect identity of the species, but his description shows 

 clearly that his specimens must belong to the same group of grap- 

 tolites. G. Sedgewickii is found in Dumfrieshire in Scotland in the 

 Lower Llandeilo slates, far below the horizon of the Hudson River 

 Giou^. D. flahelliformis very closely resembles a Quebec species. Set- 

 ting aside all questions as to the identity of the species,it is an interest- 

 ing fact that a naturalist in Russia should find below rocks which 

 represent the limestones of the upper half of the Champlain group, a 



