430 NEW YORK STATE MUSEUM 



mil scum of the Canadian Geological Survey at Ottawa, proved to 

 be a i-ather poor fragment of a siphiincle. It shows a greater rate 

 of growth than that of P. explanator and is not so flat in 

 section as the latter. 



Family CYRTENDOCER^2!>.'riDAE 



Genus cyrtendoceras Remele 

 Cyrtendoceras (?) priscum sp. nov. 



Plate 2, figure 2-5 



I obtained in the dolomite of the Beekmantown beds D at the 

 Spelman ledge at Beekmantown half a dozen specimens of a small 

 gyroceran cephalopod, that has the distinction of being the earliest 

 coiled form known from this State, and of possessing very primi- 

 tive characters which correspond to its early appearance. 



Description. Small gyroceracones attaining a diameter of but 13 

 mm consisting of about two volutions which grow at a rapid rate 

 (diameter of second volution 4 mm), possess circular sections without 

 impressed zone and though but leaving a small interspace are ap- 

 parently not coming into actual contact. Living chamber short, 

 not more than one half volution. Aperture protracted along the 

 dorsal line and provided with low lateral lappets. Cameras very 

 shallow, five in the space of 5 mm in the ephebic volution ; septa 

 quite convex, their depth equal to that of the cameras ; sutures 

 apparently straight all around. Siphuncle large, fully one third the 

 width of the conch, tubular, subdorsan in position, filled with 

 organic deposits (?). Surface without sculpturing except that 

 provided by faint growth lines. 



Observations. Unfortunately all specimens which we were able 

 to obtain are preserved only as molds, the conchs having been dis- 

 solved and the interspaces filled with a sandy matrix, the result of 

 the disintegration of the sandy dolomite. While this mode of preser- 

 vation gives good sculpture casts of the surface and of the aperture 

 it has left us in some doubt about the siphuncle. The figures show 

 that a wide empty space is left between the fdlings of the chamber- 

 spaces and the dorsal wall, which can only have been occupied by 

 the siphuncle, since there is no trace of a smaller siphuncle 

 perforating the septal fillings. Since in this rock all mollusk shells 

 are dissolved, while the interspaces are always found to be filled 

 with the dolomitic matrix, we have concluded that the siphuncle 

 which here is dissolved out entirely must have been filled with or- 

 ganic carbonate of lime. 



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