38 ' NEW YORK STATE MUSEUM 



cites an undescribed species of Hyolithus from two horizons. 1 

 (Group 6) 



HYOLITHELLUS BillingS 



Hyolithellus micans Billings. Can. nat. 2d ser. 1871. 4:215 



PI. 2, fig. 11 



The highly characteristic internal cast of the operculum of 

 this species, showing very distinctly the subcentral knob and 

 the radiating elongate ovate scars and smooth margin, was 

 found in a limestone pebble from Rysedorph hill, differing from 

 the rest of the limestone pebbles in lithologic appearance. The 

 specimen retains a part of the periderm and a fragment of the 

 shell and this indicates, as the appearance of the limestone 

 would suggest, that the lower Cambric conglomerate limestone 

 of Troy, a few miles to the north, which contains this prob- 

 lematic fossil in considerable number, is very sparingly repre- 

 sented in the Rysedorph hill conglomerate. This older Cambric 

 conglomerate has also been found by Ford at Schodack Landing, 

 with Hyolithellus micans and other species, and has r 

 therefore, a similar extension as the Trenton limestone con- 

 glomerate, with which it strikes parallel but farther east on the 

 other side of the overthrust fault. As we shall presently 

 observe, the Trenton conglomerate limestone is similar in other 

 features to the Cambric limestone at Troy and indicates a repeti- 

 tion of the conditions of early Cambric time, in the lower Siluric 

 of the same region. (Group 1) 



conularia Miller 



Conularia cf. trentonensis Hall. Pal. N. Y. 1847. 1:222 



A very young specimen of Conularia was found in a black 

 limestone from the Moordener kill conglomerate. It shows only 

 the transverse ridges; the direction and the strong development 

 of these, however, are very suggestive of identity with 

 Conularia trentonensis Hall. (Group 5) 



1 N. Y. acad. sci. Trans. 15:94. 



