REPORT OF THE STATE PALEONTOLOGIST I903 325 



length of the funnels, and the presence or absence of the inner 

 siphuncular lining, our form would have to be brought under 

 Cameroceras. We would then be in the peculiar situation of 

 having three groups of species belonging to three different gen- 

 era which have in common large preseptal apical cones or 

 nepionic bulbs, indicating long continuation of a very primitive 

 condition in early youth of the forms. In at least two of these 

 genera these primitive groups contrast with the larger number 

 of the younger congeners, in which the siphuncle has been en- 

 tirely inclosed into the phragmocone and the preseptal cone 

 superseded. 



While we do not intend to question Hyatt's view which 

 clearly considers the genus Nanno with the scope and definition 

 given to it by Clarke and Holm, as of polyphyletic origin, and 

 therefore restricts it to Nanno aulema, we are also con- 

 vinced that it would not serve the ends of a proper delimitation 

 of closely related and equally advanced forms, if one would 

 include in these three genera the forms which clearly represent 

 an older phylogenetic stage than the genotypes. For this reason 

 we propose to separate these phylonepionic forms characterized 

 by preseptal cones from the later and typical phylephebic con- 

 geners and designate them as subgenera by the prefix " protero." 

 \\"e thus have a " Proterocameroceras " represented by P r o - 

 terocameroceras brainerdi, which is a Cameroceras 

 wdth a large preseptal cone or nepionic bulb ; and a " Protero- 

 vaginoceras," which is a Vaginoceras with a like cone. To the 

 latter would have to be referred Endoceras (Nanno) 

 b e 1 e m n i t i f o r m e Holm, while the position of E. (N a n n o) 

 fistula Holm and E. (Nanno) p y g m a e u s Holm is 

 uncertain till their siphuncular structures have been studied. As 

 the long, stafflike, cylindric conchs would indicate, they may 

 belong to neither of the tw^o genera mentioned and be rather 

 genuine Nannos or come under Hyatt's genus Narthecoceras. 

 In the latter case we might have a third genus with " protero " 

 forms and later forms. 



It is in line with the more primitive character of Protero- 

 cameroceras brainerdi that it occurs in the Beekman- 

 town formation ; while Cameroceras does not find its principal 

 development till the Black river and Trenton stages. 



