490 



NEW YORK STATE MUSEUM 



The sutures are apparently straight transverse or nearly so ; the 

 septa very shallow, their concavity only two thirds as much as the 

 depth of the cameras notwithstanding their slight forward arching 

 on the convex side of the phragmocone. 



The siphuncle is highly nummuloidal, centren in position, and 

 possesses a width of 5 to 7 mm. In the early stages it is filled with 

 rings of organic deposits, forming around the septal necks and leav- 

 ing but a narrow endosiphotube open, which widens in oral 

 direction. The septal necks are very short. The septal walls, adjoin- 

 ing the siphuncle are thickened by radiating deposits in correspond- 

 ence to the internal deposits of the siphuncle. The surface is 

 smooth or only possessed with such faint sculpture as the growth 

 lines furnish. 



Position and localities. The type specimen comes from the 

 dove-colored Chazy limestone (cited in the original description as 

 the dove-colored limestone of the Birdseye) at Isle La Motte, Lake 



V: 



Fig. 45 Fig. 46 Fig. 47 _ 



Fig. 45 Cyrtactinoceras boycii Whitf. (sp.) Section of fragment, showing 



part of living chamber. Valcour Island. Natural size. _ 



Fig. 46 Cyrtactinoceras boycii Whitf. (sp.) Longitudinal section of frag- 

 ment showing siphuncle. x% ^ . „ 

 Fig. 47 Cyrtactinoceras boycii Whitf. (.sp.) Transverse section. -Xxo 



Champlain. I have found another specimen from the same horizon 

 in the Perkins collection of Isle La Motte fossils in Burlington 

 University ; and one from the dove-colored limestone of Valcour 

 island is figured here. I have also collected three specimens in the 

 Strephochetus beds of B^ and of C^ at Chazy village. 



