302 NEW YORK STATE MUSEUM 



siphuncle," and adds, " This plate shows at intervals slight pro- 

 jections giving rise to delicate cones apparently membranous." 

 Hyatt [1884, p.266], though basing his definition of Piloceras 

 on Dawson's description, did not recognize the presence of a parti- 

 tion, but believing in its tubular character, referred it to the endosi- 

 phuncle. Foord, however, observed again the same plate in a 

 Piloceras from Durness and figured it [1888, p. 159, fig. 17, HI, 

 p. 1 60], stating in regard to it in opposition to Hyatt's view: 

 " Nevertheless there seems to have been an internal septum 

 extending upwards, from the lower part of the siphuncle, between 

 the wall of the latter and that of the sheath into which the 

 endosiphon opens. This septum shows itself in some transverse 

 sections of the siphuncle in the manner indicated at figure 17, H 



[copied here in text fig.3], and it can be 

 traced for some distance upwards in the 

 vertical section of this and of other speci- 

 mens. The septum seems to have been 

 penetrated by the endosiphon, as shown in 

 Fig. 3 Piloceras sp. the fisfure, but I am unable to give any 



Transverse section of siphuncle. o ;- o ^ 



fcopy from'poir'd)^' partition, satisfactory accouut of it, owiug to its im- 

 perfect condition." Bather later [1894, 

 p.433] copied Foord's figure, stating that the appearance of the par- 

 tition is exaggerated and its significance unknown. Specimens of 

 Piloceras explanator from the Fort Cassin bed, which 

 are in the State Museum, show the same partition and we shall have 

 occasion to recur to its structure [see p.329]. 



Meanwhile Holm had found a similar endosiphuncular blade 

 strongly developed in a species from Esthonia, which he described 

 in allusion to this feature as Endoceras gladius [1887, 

 p. 1 3]. In this important publication, to which we shall have frequent 

 occasion to refer, Dewitz's observation of the winglike membranes 

 of the endosiphuncle, is verified. 



In a later publication [1895, P-6o5ff] the same author has 

 introduced a number of terms for the parts of the siphuncle in 

 view of the fact that Bather had criticized Hyatt's term " endo- 

 siphon " [/. c, p.433] arguing that the '' endosiphon " is in func- 



