272 bulletin: museum of comparative zoology. 



These genera may be divided into two groups, first those appearing 

 first in the Walchow and Kunda in Russia, and second, those making 

 their first appearance in the Wierland in Russia. In the first group we 

 find Eoharpes (also in Beekmantown), Remopleurides, Nileus, 

 Ceraurus, Xieszkowskia, and Pterygometopus. In the second group 

 are only Lonchodomas, Pseudosphaerexochus, Sphaerexochus, and 

 Sphaerocoryphe. Cybeloides, Pliomerops, Vogdesia, and Heliomera 

 are all derived from forms appearing first in the lower group in Russia. 



From this analysis of the Chazy fauna it appears that, while the 

 fauna is in very large proportion of American origin, it has present in 

 it a considerable Russian element which is largely derived from genera 

 present in the Walchow and Kunda formations. Why certain genera 

 such as Echinosphaerites, Oxoplecia, Plectambonites, and Christiania 

 from Russia, and Tretaspis, Nidulites, and Agnostus from Scandi- 

 navia, which reached North America somewhere about this time, did 

 not get into the typical Chaz}' is a perplexing question. So far as 

 bottom control is concerned, there seems to have been no barrier, and 

 only two possible explanations occur, namely, either their natural 

 habitat was fully occupied, or they did not reach America till later 

 than the time of the typical Chazy; the latter explanation seems, in 

 view of all the facts, the more probable. 



DETAILED SECTIONS IN RUSSIA. 



Sections arranged in order from east to west. 

 Section on the W^alchow. (Given by Lamansky (29)). 



Biii^. Thick-bedded compact limestone at Sapolek and 

 Bylstchina, and at the base of the quarries at St. Mich- 

 ael Archangel. 6 meters = 18.35 m. 



B,ii,3. Rusty and spotted limestone at the base, followed 

 by one or more layers of " Linsenschicht," these being 

 succeeded by red and yellow spotted layers. The Linsen- 

 schicht is one meter above the base. 3.5 m. = 12.35 m. 



Bina- Bluish green limestone with fine-grained glauconite at 



the base, but none above. 3 m. = 8.85 m. 



B,i^. Compact limestone with some glauconite. Loses 



compactness quickly on weathering. 2.4 to 2.7 m. = 5.85 m. 



