REPORT OF THE STATE PALEONTOLOGIST I9O3 339 



stage of development with a prominent nepionic bulb, which fact is 

 of sufficient phylogenetic importance to require recognition by 

 assigning these forms to subgenera (Proterocameroceras, Protero- 

 vaginoceras and possibly Proteropiloceras) of their respective 

 genera. 



9 The endosiphocoleon is revived in the proostracum of the 

 belemnites, the probable Mesozoic descendants of the Paleozoic 

 holochoanitic and orthochoanitic orthoceraconic cephalopods. 



10 In Piloceras explanator Whitfield the nepionic 

 bulb is still recognizable by an inflation of the apical portion of 

 the siphuncle, which by tachygenesis has become inclosed in the 

 phragmocone. 



11 The endosiphocoleon extends without becoming absorbed 

 to or nearly to the apical end. This results from the wide short 

 form of the siphuncle. 



12 The endosiphosheaths and endosiphocoleon are held in posi- 

 tion by numerous suspensory funicles (endosiphofunicles). These 

 proceed from angulations of the endosiphosheaths and frequently 

 divide in outward direction. 



13 The arrangement of the endosiphofunicles on the side oppo- 

 site the flat side of the conch, where siphuncle and conch are in 

 contact, indicates that this latter side may have been the ventral 

 one and that the conch was carried in a subhorizontal, slightly 

 ascending direction. 



14 Piloceras newton-winchelli Clarke is by the 

 structure of its ectosiphuncle not a holochoanitic form as the 

 other congeners, but an orthochoanitic form and represents a 

 genus (Clarkoceras) which holds the same relation to Piloceras 

 as Baltoceras to Endoceras. 



References 

 1867 Barrande, J. Systeme Silurien de la Boheme, v.2. Cephalo- 



podes (1867-77), t.430, f.5, 8-11 ; t.471, f.8-io. 

 1879 Dewitz, H: Beitrage zur Kenntniss der in den ostpreussi- 



schen Silurgeschieben vorkommenden Cephalopoden. 



Schriften der physik.-oekon. Gesellsch. in Konigsberg. 



Bd2o. 



