270 



Report of the State Geologist. 



Genus Chonetes, Fisher. 



96. Chonetes mucronata, Hall. 



1867, Hall, Pal. N. Y., vol. 4, p. 125, pi. 20, 21. 



This form is not very common at Eighteen-mile creek, where it is mainly 

 restricted to the lower Moscow shales. Several specimens were obtained from 

 the shales and limestones below the Trilobite beds, the species occurring at 

 intervals down to, and in the Marcellus shales. The variety laticosta 

 occurs occasionally, and this latter form is also found in the Encrinal lime 

 stone. The various specimens from the Moscow shales show gradations 

 between this and the next form, suggesting the possibility that the two 

 represent different phases of one and the same species. 



97. Chonetes deflecta, Hall. 



1867, Hall, Pal. N. Y., vol. 4, p. 126, pi. 21. 



This species occurs abundantly in the lower Moscow shales, between two 

 and three feet above the Encrinal limestone. The specimens are large, very 

 convex, and closely striated by numerous rounded, rather coarse striae. 

 Specimens showing the laterally deflected spines like those of C. mucronata, 

 are not uncommon. Examples also occur which show an approximation in 

 their striae to the latter form, suggesting the possible identity of the two, as 

 intimated by Professor Hall. A few specimens from the Encrinal limestone 

 have been referred to this species. It appears to be absent from the shales down 

 to the Trilobite beds, below which it is occasionally found. No specimens 

 have been noticed below the Strophalosia bed. 



98. Chonetes setigera, Hall. 



1867, Hall, Pal. N. Y., vol. 4, p. 129, pi. 21. 



This species is rare at Eighteen-mile creek. A specimen showing the 

 characteristic spines and form has fewer striae. It was found two or three 

 feet below the Encrinal limestone at Section C. Two specimens from Section 

 B, seventeen to twenty-one feet below the Encrinal limestone, are probably of 

 this species. In the lower beds of the group it is somewhat more abundant, 

 specimens having been obtained in the Pleurodictyum layers, and in the 

 transition shales on the lake shore down to twelve feet below the Strophalosia 

 bed. 



