CATALOGUE 
OF 
FOSSIL CEPHALOPODA. 
Phylum MOLLUSC A. 
Class CEPHALOPODA. 
Order TETRAB RANCHI ATA. 
Suborder NAUTILOIDEA. 
(Suture-line simple, more rarely undulating or denticulate. 
Siphuncle variable in position. Septa concave towards the aper- 
ture. I^ecks of septa usually short {ERlipoclioanoida, Hyatt), more 
rarely long {Holochoanoida \ Hyatt). Initial chamber conical, with 
cicatrix.) 
Family ORTHOCERATID^. 
Genus ORTHOCERAS, Breynl 
{Molossusj Achelois, Month 1808.) 
Gen. Char. Shell straight or slightly curved, elongate-conical, 
circular or subelliptical in cross-section. Septa concave, usually 
horizontal, sometimes a little oblique ; widely separated as a rule. 
Siphuncle usually slender, cylindrical, central, subcentral, or eccen- 
tric. Body-chamber large, of variable length. Aperture simple. 
^ Embracing Endoceras, Piloceras, and some other aberrant genera. 
^ Dissert. Phys. de Polythalamiis, 1732, Cap. vi. p. 28. 
B 
