HUDSON RIVER GROUP. 

 9. 



65 



There are many other fossils, also, which exclusively belong to this rock, some of which 

 are equally characteristic ; such as the Modiolar cypricardite (Cypricardites modiolaris), the 

 Narrow-front cypricardite (C. angustifrons), the Nasal cypricardite (C. nasuta), the Ovate 

 cypricardite (C. ovata), the Curtate cypricardite (C. curta), the Pholade orthonata (O. pho- 

 ladis), and some others not yet described, among which is an orthoceras highly characteristic 

 of this rock.* 



Besides these fossils, there are others which belong also to the Trenton limestone, but 

 which do not appear in the Frankfort slate or rubblestone either in the district or in the counties 

 of Schenectady or Schoharie, though the mass is of such great thickness in those two coun- 

 ties, exceeding five hundred feet. This mass appears to thin out to the west, by which 

 means the longer-lived races were enabled to continue their existence, or rather extend their 

 range from the lower to the higher rOck. The fossils which reappear, as it were, in the dis- 

 trict, cire the Semioval strophomena. Alternate strophomena, Tortoise orthis and Senior caly- 

 mene. Besides these, there are two others of which doubts exist as to identity, the individuals 

 of both very numerous in both rocks, the Tessellated cryptolithus and the Open bellerophon. 

 It may be well to state that the Tessellated cryptolithus, which was found in every locality 

 of the sub-mass or lower portion of the upper division, was not often seen in the upper portion. 



The mineral character of the division at Pulaski is about the medium one of the district, 

 consisting of dark grey-colored sandstone and bluish shale, the two more or less intermixed 

 with each other. Some portions of both are mixed with carbonate of lime, and also with 

 pyrites ; the latter is evidenced on those parts containing calcareous fossils, which for a long 

 time have been exposed to the weather, being more or less stained with iron. The rock forms 

 a low bluff on both sides of the river, its greatest height about twenty-five feet ; and continues 

 down the stream for some distance. Above the dam at the village it is uncovered on the 

 north shore, rising but a few feet above the river. Higher up, about a quarter of a mile from 



•The whole of theao species of Cypricardites, as well as the Orthonata, were noticed in the annual repoiis under the generic 

 name of Pterinea, 



Geol. 3d Dist. 9 



