CLASS V 



CEPHALOPODA 



595 



Orthochoanites and Cyrtochoanites. The characters of these different groups are defined 

 under tlieir proper headings. 



Suborder A. HOLOCHOANITES Hyatt. 



Funnels of siphuncular segments reaching from the septum of origination to the plane 

 of the next septum apicad or heyond this, or in some geyiera even to the plane of the second 

 septum. 



I. DiPHRAGMiDA Hyatt. 



This groiip contains biit one family, Diphragmidae, having the same characters as 

 the following uniqiie genus : — 



Diphragmoceras Hyatt. Orthoceracones and cyrtoceracones having simple septa 

 and sutures as in Endoceratida, but siphnncle divided by tabnlae alternating with the 

 septa of the camerated shell. Chambers of siphuncle empty, as are also the camerae. 

 Quebec group. 



II. Endoceratida Hyatt, 



Orthoceracones, cyrtoceracones, gyroceracones and nautilicones having siphuncles of 

 variable diameter, but as a rule large in proportion to the width of the shell. They may he 

 empty or filled ivith internal organic deposits, but are invariably tubulär, and the funnels 

 completely shut off the interior from the interiors of the camerae. The latter are without 

 organic deposits. 



Family 1. Endoceratidae Hyatt. 



Smooth or annulated orthoceracones. Siphuncle alivays more or less filled with 

 organic deposits. 



A B C 



Fio. 1104. 

 A, Vaghiocems duplex (Wahlenberg). Ordovician ; Kinneknlle, 

 Sweden. Mach reduced. B, V. commune (Wahlb.), Ordovician ; 

 Oranienbaum, Russia. The anterior endocone of the siphuncle is 

 filled up with niatrix so as to form a dart (" Spiess "). 1/2- ^', !>>«- 

 gramniatic longitiulinal section of the last, showing siphonal 

 funnels. D, Detached caraera of Vcußnoceras with long siphonal 

 funnel. (Figs. C and D after Dewitz.) 



Fig. 1105. 



Endoceras proteiforme Hall. Ordovi- 

 cian ; New York. Longitudinal section 

 showing funnels and endocones. 



Vaginoceras Hyatt (Fig. 1104). Ordovician. Cameroceras Conrad {Sannionites 

 Fischer von Waldheim ; Suecoceras Holm). Ordovician and Silurian. 



Endoceras Hall {Golpoceras Hall; Diploceras Conrad) (Fig. 1105). Smooth or 



