252 



Report of the State Geologist. 



Genus Pterinea, Goldfnss. 

 40. Pterixea flabella, Conrad. 

 1884, Hall, Pal. N. Y., vol. 5, pt. 1, p. 93, pi. 14, 15, 83. 



This species is common in the S. rfemissa beds, where it preserves its 

 surface markings to a considerable extent. The shell is thin and fragile, 

 never attaining the thickness which this species presents in the eastern part 

 of the state, where the shales are more arenaceous. The specimens are also 

 usually smaller than the average size. Several specimens obtained are very 

 oblique, almost resembling in this respect the next species enumerated ; the 

 surface markings, however, are typical. It is not an uncommon form, in the 

 shale immediately above the S. demissa bed (Stictopora bed). Several frag- 

 ments were obtained from the shale down to twelve feet below the Encrina! 

 limestone. The species however is practically restricted to the upper one foot 

 of the Hamilton shales. 



Genus Actinopteria ( Hall. 



41. Actixopteria decussata, Hall. 



1884, Hall, Pal. N. Y., vol. 5, pt. 1, p. Ill, pis, 17, 18, 20, 84. 



This is not an uncommon form in the Encrinal limestone, where the 

 specimens are often large. Though often somewhat effaced, the character, 

 istic surface markings can usually be made out. Fragments of this species 

 also occur in the upper foot of the Hamilton shale beneath the Encrinal lime- 

 stone, while occasional representatives of the species are found in the 

 Pleurodictyum beds of Avery's creek and the lake shore. The intermediate 

 shales have not furnished any specimens, nor have any been found above the 

 Encrinal limestone. 



42. Actixopteria Boydi, Hall. 



1884, Hall, Pal. N. Y., vol. 5, pt. 1, p. 113, pis. 19, 84. 



This species is rare in our district. A few specimens were found in the 

 Pleurodictyum layers of Avery's creek and the lake shore. 



Genus Leiopteria, Hall. 



43. Leiopteria Raflxesquei, Hall. 



1884, Hall, Pal. X. Y., vol. 5, pt. 1, p. 161, pL 15, 20, 88. 



This species is represented by a single left valve, rather imperfect, but 

 show ing the characteristic form and surface markings. It was found in the 

 S. <1c.iiiias<i bed. 



