404 NEW YORK STATE MUSEUM 



to the next septal neck or beyond. The inside of this siphimcular 

 wall is sometimes still covered by another layer of organic deposit, 

 the cndosiplwlining. 



Forms in which the ectosiphimcle is composed only of septal 

 necks are called holochoanitic (order Holochoanites) ; those in which 

 the septal necks are short but straight, orthochoanitic (order Ortho- 

 choanites) and those in which the septal necks are short and bent 

 outward or crumpled, cyrtochoanitic (order Cyrtochoanites). 



Order NAUXILOIDE^A. 



Suborder A HOLOCHOANITES Hyatt 

 Division II ENDOCERATIDA 

 Family endocer^^tid^j^e 



Genus cameroceras (Conrad) emend. Hyatt 



This genus was defined by Conrad in the following diagnosis : 

 Straight ; siphuncle marginal ; a longitudinal septum, forming a 

 roll or involution with the margin of the siphuncle. 



Hall recognized the genus stating that he found no evidence of 

 the longitudinal septum and, seeing its generic character in the 

 '■ oval form of the shell ", restricted the term to Conrad's genotype 

 Cameroceras trentonense erecting a new genus Endoc- 

 eras for the many similar forms of the Trenton with a different 

 section. The latter name has found very wide acceptance and 

 Cameroceras treated as a synonym of Endoceras \^see Foord, 1888, 

 p. 129] ; while others, inclined to recognize the right of priority, 

 have referred the whole group of forms with long septal necks and 

 endosiphuncular organic deposits to Cameroceras {see Clarke, 1897, 



P-775]- 



Hyatt has from the beginning [1884, p. 266] held that three 

 genera could be differentiated in this group of obviously closely 

 related forms, viz Vaginoceras (Hyatt), Endoceras (Hall) and 

 Sannionites (Fischer de Waldheim). The latter term he has later 

 on replaced by Cameroceras. The principal diagnostic characters of 

 Vaginoceras are seen in the posterior extension of the septal necks 

 beyond the next preceding septum and the great number of endo- 

 siphosheaths ; those of Endoceras in the posterior extension of the 

 septal necks to the next septum only, the smaller number of endo- 

 siphosheatbs and the absence of an internal lining laver in the 

 siphuncle (endosipholining) ; those of Cameroceras in the presence 

 of one large thick walled sheath only in connection with the living 



