514 MOLLUSCA SUB-KINGDOM VI 
or cicatriz, which is more or less compressed elliptical, never transversely elliptical or 
depressed, and is sometimes hidden by the protoconch or tts shrunken remnants. 
The order may be subdivided according to the general external features of 
the shell and structure of the siphunecle into five sub-orders, as follows, named with 
reference to peculiarities of the funnels :—Holochoanites, Mixochoanites, Schistochoanites; 
Orthochoanites, Cyrtochoanites. The characters of these different groups are defined 
under their proper headings. 
Sub-Order A. HOLOCHOANITES. Hyatt. 
Funnels of siphuncular segments reaching from the septum of origination to the plane 
of the next septum apicad or beyond this, or in some genera even to the plane of the second 
septum. 
I. DIPHRAGMIDA. 
This group contains but one family, Diphragmidae, having the same characters as 
the following unique genus :— 
Diphragmoceras, Hyatt. Orthoceracones and cyrtoceracones having simple septa 
and sutures as in Lndoceratida, but siphuncle divided by tabulae alternating with the 
septa of the camerated shell. Chambers of siphuncle empty, as are also the camerae. 
Quebec Group. 
Il. ENDOCERATIDA. 
Orthoceracones, cyrtoceracones, gyroceracones, and nautilicones having siphwneles of 
variable diameter, but as a rule large in proportion to width of the shell. They may be 
empty or filled with internal 
organic deposits, but are in- 
variably tubular, and the 
funnels completely shut off the 
interior from the interiors of 
the camerae. The latter are 
without organie deposits, 
Family 1. Endoceratidae. 
Smooth or annulated ortho- 
ceracones.  Siphuncle always 
more or less filled with organte 
deposits. 
Vaginoceras, Hyatt (Fig. 
1055). Ordovician. Camero- 
ceras, Conrad (Sannionites, 
Hyatt ;  Sweeoceras, Holm). 
Ordovician and Silurian. 
Endoceras, Hall (Colpo- 
ceras, Hall; Diploceras, Con- 
A, Vaginoceras (End.) duplex, Wahlb. Ordovician; Kinnekulle, ibe eS ee it , 
Sweden. Muchreduced. B,V.commune, Wahlb. Ordovician’ Oranien- rad), (Fig. 1056). Smooth 
baum, Russia. The anterior endocone of the siphuncle is filled up , > 7 ETA. . 
with matrix so as to form a dart (“Spiess”). 1/o. C, Diagrammatic ug annulated orthoceracones. 
longitudinal section of the last, showing siphonal funnels. D,De- Funnels reach from septum 
tached camera of Vaginoceras with long siphonal funnel. (Figs. C . ay : a 
and D after Dewitz.) 5 5 of origination to the next 
apicad of this, but mo farther. 
Septa pass entirely around the siphuncle. Organic deposits in the form of endocones, 

Fic. 1055. 

