20 Calciferous of the Mohawk Valley 132 



It may be a variety of C. micros^opicum Dwight^'S but is larger 

 and has wider air chambers. C. didys Billingst, is a larger shell, 

 the septa in a shell twice as large as ours has air chambers of the 

 same size. 



Locality. — Found in bed V 2, near Ft. Hunter, N. Y. 



ORTHOCERAS Breynius 



Orthocera's primigenium Vannxem 



PaL N. Y., vol. I, [S47, p. 13, PI. 3. 

 Am. M. N. H., Bull., vol. 2, p. 56, PI. 10. 



Hall's description is "elongated, terete, gradually tapering 

 to an obtuse point; seclion circular; septa thin, deeply concave, 

 closely approximated, being distant only 1-25 the diameter " 



A few imperfect specimens were fourid in the Ft. Hunter 

 secftion. No- II 3 



Pelecypoda 



RIBEIRIA Sharpe 



The class relationship of this genus has been discussed both 

 b}^ Billings and Whitfield. 



In the original description of the genus Sharpe (Geol. Jour., 

 vol. 9, p. 157, PI. 9, 1853) ^ays- "This curious shell appears re- 

 lated to the family Calyptrgeidse ^ * * It is equilateral, and 

 both the transverse internal plate and muscular attachment are 

 placed along the middle of the back of the shell; the external 

 form ma}' be described as a Calyptrsea pressed together laterally 

 till the sides nearly meet, leaving only a narrow opening for the 

 foot of the animal." 



Billings (Pal. .Fos. vol. i, 1S61-65, p. 339) states that "in 

 general characfler his .species agrees with the descriptions of 

 Sharpe, but that the internal cast does not exhibit the muscular 

 impression." 



"Am. Jour. Science, 3rd series, vol. 27, p. 256, fig. 11. 

 tPal. Fos., vol. I, p. 192, fig. 176. 



