.BEEKMANTOWN AND CHAZY FORMATIONS OF CHAMPLAIN BASIN 45 1 



of the cameras. Surface smooth, internal surface of outer wall 

 marked with fine engirdling lines. 



Position and localities. Frequent in the Fort Cassin beds at 

 Fort Cassin; rare in the same beds at Valcour N. Y. (A3 of 

 section). 



Observations. This species is one of great mor- 

 phologic and phylogenetic interest in many respects. 

 The most important of these is the presence of in- 

 terior annulations (or constrictions) upon the 

 •conch which have not yet had any effect 

 upon the outer side of the conch, the lat- 

 ter showing only in exceptional cases, 

 faint transverse elevations upon the liv- ^9 -° 



ing chamber \see fig. 7, 81. These in- ^''s- ^9 w?-^7F°^^x^' cornu- 



o I- &/'j oryx Whitf. (sp.) Transverse sec- 



ternal constrictions have been mistaken t'°"- ^""■'f,^'%^- /?^; ^° f^"^^- 



Enlargement (X4) of siphuncle 



hy Whitfield for external annulations of 



the conch and the species described as strongly annulated. The form 

 of the supposed annulations as they appear upon the inner cast of 

 the conch is however greatly dift"erent from that of the true annu- 

 lations of most orthoceratites and has led to the specific name. 



Note on the nautilicones of the Beekmantown and Chazy 



formations 



Professor Whitfield has described among the Fort Cassin fossils 

 two species of Nautilus, viz, Nautilus k e 1 1 o g g i and N . ? 

 champlainensis. Since we have a considerable number of 

 specimens from the \'alcour outcrops, which clearly fall within the 

 boundaries of these species, we have to occupy ourselves with the 

 vicissitudes of the latter. Schroder pointed out soon after the pub- 

 lication of the species [1891, p. 27] that the original description 

 and the drawings of the first named one do not agree with each 

 other and that it is to be inferred that specimens which have not 

 been figured were used for the description. Since the former of 

 these drawings [/. c. pi. 30, fig. i] which represents a large and 

 perfect specimen is designated as illustrating the type specimen 

 in the explanation of the plate, the other two have to be considered 

 as belonging to another species. They have been made by Hyatt 

 the types of his new species E u r y s t o m i t e s r o t u n d u s 

 [1894, p. 443]. In the last cited work there is described still a 

 third form, viz, E u r y s t o m i t e s v i r g i n i a n u s as probably 

 comprised by Whitfield's original description, but as not being 

 figured by him. We have therefore altogether probably three 

 species in the Fort Cassin beds which were originally described 



