454 



NEW YORK STATE MUSEUM 



2 Synoptic table of the nautilicones of the Chazy formation in New 



York and Canada 



SPECIES DESCRIBED 

 BY BILLINGS 



SPECIES DESCRIBED BY 

 HYATT 



SPECIES NOTED IN NEW YORK 

 BY THE AUTHOR 



Nautilus natator. . 

 N. tyrans 



Barrandeoceras natator.. 

 B. minganense 



Plectoceras jason 



Barrandeoceras natator 



Tarphyceras multicameratum 

 Deltoceras van ingeni 

 Plectoceras jason 



Division II. PLECTOCERATIDA 

 Family tarphyceratidae 

 Genus barrandeoceras Hyatt 

 This genus has been diagnosed in the Genera of Fossil Cephalo- 

 pods [1884, P- 2 99] as follows: 



Gyroceran and nautilian shells with very large umbilical perfora- 

 tions, and compressed, slightly costated or smooth whorls, generally 

 without an impressed zone, though this is sometimes present. The 

 venter is narrower than the dorsum, the siphon near but above the 

 center, septa deeply concave, and sutures with ventral saddles, lateral 

 lobes and dorsal saddles, without annular lobes. Type, Barr. 

 (Naut.) natator sp. Bill. Living chamber is about one half 

 of a volution in length ; it is about three fourths of a volution in 

 length in the type species. 



Later on [1894] it has been added that the lobation here described, 

 is only found in forms having the gyroceran mode of coiling, but 

 not in those which have the closer nautilian form. Since we are 

 here concerned with the genotype only, which is a gyroceran form, 

 we need not enter upon these variations of lobation. 



Barrandeoceras natator Billings (sp.) 



Plates 1,2 and 33 



Nautilus n a t a t r Billings. Can. Nat. 1859. v. 4, no. 6, p. 466 

 Barrandeoceras natator Hyatt. Bost. Soc. Nat. Hist. Proc. 1884. 

 22:299 



Barrandeoceras natator Hyatt. Am. Phil. Soc. Proc. 1894. 32:452 

 Hyatt's description of this species, which contains most of the 

 essential characters, is this : 



This species has volutions compressed oval in section, the dorsum 

 somewhat broader than the venter; siphuncle is extracentroventran, 

 even in the neanic stage ; septa deeply concave ; sutures with dorsal 



