166 Annals of the Carnegie Museu.m. 



Hamilton at Thedford, and below the Encrinal at Eighteen Mile 

 Creek. 



Cm /lie //a liaiiiiltouice Hall. 



Pal. N. Y., Vol. IV, 1867, p. 27, pi. 3, figs. 17-23. 



This species is fairly common in the material and presents the 

 usual characters. The largest specimen is 15.2 x 19 mm. The 

 dorsal valves show a variety of markings, varying with the shell to 

 which they were attached. Most of them show the coarse ribbing of 

 jyopidoleptus or Spirifer. The species does not seem to be common 

 very often, but is found from Thedford to Otsego Co. 



Stropheodonta concava Hall. 



Pal. N. Y., Vol. IV, 1867, p. 96, ])1. 16, figs, \a-\h. 



This species is very rare in the locality. One dorsal valve of an 

 adult individual was found, and two or three shells of younger speci- 

 mens. The species is found in all sections from Thedford to Otsego 

 Co., but is seldom common. 



S. demissa Conrad. 



Pal. N. Y., Vol. IV., 1867, p. loi, pi. 17. 



This species is found from Thedford to Cayuga Lake, but its verti- 

 cal range in the various sections is very limited and it cannot be 

 called a common fossil except on its western range where it is com- 

 mon in certain zones. At Thedford it is very rare below the Encri- 

 nal, but common in two of the zones above it. At Eighteen Mile 

 Creek it occurs in shale a foot below the Encrinal and in the lime- 

 stone itself. At Livonia it is restricted to the Encrinal and at Cayuga 

 Lake to a single zone about 50 feet below the Encrinal. It is a very 

 rare fossil at Canandaigua Lake. 



S. inccqicistriata Conrad. 



Pal. N. Y., Vol. IV., 1867, p. 93, pi. 12, figs 6-8. 



In all sections from Eighteen Mile Creek to Otsego Co., this fossil 

 is common, and in the present faunule is represented by about 600 

 specimens which show no unusual characters. 



S. jiinia Hall. 



Pal. N. Y., Vol. IV., 1867, p. 108, pi. 18, figs. 3, 4. 



Only one specimen which could be referred to this species was 

 found. It has been reported from the Lower Hamilton at Eighteen 

 Mile Creek and from the very top at Livonia and Cayuga Lake. 



