1821.] Geological Society. 75 



bottom : below is a black sandy clay, mingled with pyrites, and 

 connected with a rugged ironstone, which contains charred wood. 

 About six versts above the town of Borovichy is the lower fall, 

 where the sand appears in horizontal strata, containing thick and 

 regular beds of an argillaceous ironstone, which is an agglome- 

 rate of charred wood and every sort of geode, resembling the 

 sandstone of the Popovca, and other streams, near Petersburg, 

 in its superficial appearance. Above is a reddish sand, and 

 below is a yellow sand, which presents a pseudo strati- 

 fied structure. The next beds are blue limestone, which 

 continues to near the water's edge, and contains madrepores, 

 resembling those of the mountain limestone in Northumberland, 

 and a very peculiar sort of Briarean Encrinite, the joints of which 

 are extremely minute. Impressions of large tufts of this encri- 

 nite cover the greater part of the surface of these limestone 

 strata, bending sometimes in one direction, and sometimes in 

 another. They are also found in the yellow and more sandy 

 variety of this limestone, which is discovered within the bed of 

 the river. The latter also contains fragments of large encrini, 

 corallines, and other marine fossils. 



At the upper fall, though the banks of the river are not so high 

 as at the lower, yet good sections of the limestone are presented. 

 It contains chert in situ, and both the limestone and chert are 

 varied with yellow and red patches, and pass gradually into 

 each other, exhibiting several fossils similar to those above- 

 mentioned. Below these beds, the pyrites and coal shale re- 

 appear at the water's edge. 



The Nista, though in many places very shallow, and obstructed 

 by rocks, is of great importance in the internal navigation of 

 Russia, as it cuts through almost the whole breadth of the Val- 

 day hills, and is joined by a canal to the Tvertza, which rises not 

 far from the source of the former, and flows southward, by which 

 means a communication between the Baltic and Caspian seas 

 has been effected. 



A paper was read, entitled, " Notice of the Discovery of a 

 New Fossil Animal, forming a link between the Ichthyosaurus 

 and Crocodile, together with general Remarks on the Osteology 

 of the Ichthyosaurus. From the Observations of H. T. De la 

 Beche, Esq. F. R. S. and M. G. S. and the Rev. W. D. Cony- 

 beare, F. It. S. and M. G. S. Communicated by the latter." 



This memoir contains a notice of the discovery of the re- 

 mains of an entirely new animal, allied to the order Lacerta, 

 among the fossil bones imbedded in the lias, to which the name 

 of Plesiosaurus has been assigned. This animal is highly inte- 

 resting, as exhibiting in its structure a link between the existing 

 genera of the above order, and the very remarkable genus Ich- 

 thyosaurus, or Proteasaurus, between which and the genus Cro- 

 codile, it would occupy an intermediate place in a natural ar- 

 rangement. The head bones of this animal yet remain to be 

 discovered. The vertebrae nearly agree with those of the era- 



