BEE K M A N TOW N AND CHAZY FORMATIONS OF CHAM PLAIN BASIN 443 



dorsocentren (situated just dorsad of the center or towards the con- 

 cave side of the conch). Xo regular deposits observed. 



The cameras are shallow, the sutures regularly transverse. The 

 septa show approximately the same closeness of arrangement as the 

 annulations and the same relation to the width of the conch. 



Position and localities. Xot infrequent in the dolomite beds be- 

 longing to D of the Beekmantown formation at the Spelman ledge 

 near Beekmantown and in A 3 of the Valcour shore section which 

 corresponds to a part of the Fort Cassin beds. Billings records this 

 form as occurring in the calciferous sandrock of the Mingan islands, 

 the township of Godmanchester, counties of Leeds and Granville ; in 

 forms referred with some doubt to this species from various localities 

 in Newfoundland, namely Cape Norman, divi- 

 sion G; Pistolet bay on Schooner island, in di- 

 vision H ; and at the river of Ponds in G. 

 Divisions G and H are supposed to represent the 

 upper part of the formation in Newfoundland. Fig. .6 Protocycio- 



_ 1 1 ceras lamarcki 



Billings states in regard to these Newfoundland Billing ( sp .) Trans- 



" ° verse section, x T 9 



specimens [p. 255] that they agree with his 

 types of O. la m a r c k i in all surface characters and the rate of 

 tapering but that the majority of the specimens possess a somewhat 

 narrower siphuncle which is only *4 the width of the conch; some 

 siphuncles however also attaining the full width of the typical speci- 

 mens. On the Mingan islands the species is recorded to be found in 

 a limestone intervening between the typical Calciferous sandrock 

 and the overlying Chazy. It seems therefore that this species may 

 range through the entire upper Beekmantown formation. 



Protocycloceras whitfieldi sp. now 



Piate 15, figure 7 



O r t h o c e r a s b i 1 i n e a t u m Whitfield. Am. Mus. Nat. Hist. Bui. 

 1890. v. 3, pl. 2, fig. 5 



Professor Whitfield has referred a closely annulated cephalopod 

 from the Fort Cassin beds to the Black river species O . b i 1 i n - 

 eat urn, arguing that a comparison of the Fort Cassin material 

 with the forms from Watertown (Black river) and from the dove- 

 colored limestone of Isle La Motte (Chazy) has not furnished any 

 criteria by which they can be distinguished. Such a forcing of forms 

 of the Beekmantown, Chazy and Trenton formations into one species 

 is however only possible on the assumption of extreme variability 

 on the part of that species; and this indeed is claimed by that emi- 



