CLASS V 



CEPHALOPODA 



60/ 



Ännular lohes ahsent except in a feto Triassic forms. Siphuncle generally more or less 

 nummuloidal. 



Family 17. Hercoceratidae Hyatt. 



Gyrtoceracones, gyroceracones, nautilicones and torticones having depressed elliptical 

 suh-quadrate or trapezoidal sections. Aperture has two deep sinuses with projecting edges 



Fig. 1120. 



Hercoceras mirum Barr. Devonian (Etage G) ; Hlubocep, Bohemla 

 (after ßarraiide). 



Ptenoceras (Gyr.) cdatum 

 (Barr.). Silurian (F) ; 

 Konieprus, Bohemia. i/i 

 (after Barrande). 



at the ventro-lateral angles, and these are usually persistent, forming two lines of more or 

 less spout-like processes. Sutures with ventral, lateral and dorsal lohes. Siphuncle 

 ventrad of centre. 



Hercoceras Barr. (Fig. 1120), Trochoceras Barr.; Ptyssoceras, Ptenoceras (Fig. 1121), 

 Anomaloceras Hyatt. Devonian. 



Family 18. Tainoceratidae Hyatt. 



Discoidal nautilicones with more or less massive volutions which at some stage or 

 throughout life are trapezoidal in section, tuherculated, and without well-deßned lateral 

 and umhilical zones. Sutures have ventral, lateral and dorsal, hut no annular lohes. 

 Spinous processes are complete, never spout-like. Siphuncle bmall, tubulär. 



Temnocheilus M'Coy {Endolohus Meek and Wortli ; Gryptoceras d'Orb.). Section 

 trapezoidal throughout life, and one row of persistent spines and nodes on either 

 side at the ventro-lateral angles. Devonian to Carboniferous. 



Foordiceras Hyatt. Permian. Metacoceras and Coelogasteroceras Hyatt. Carboni- 

 ferous. Diadiploceras Hyatt. Devonian. ' Tainoceras Hyatt. Carboniferous. 



Family 19. Oentroceratidae Hyatt. 



Gyroceracones and nautilicones with young similar to early stages of Temnocheilus 

 htfore the impressed zone is formed. Shell suhsequently hecoming tetragonal in section, 

 the venter is flattened or concave, and dorsum remaining convex until a late stage. 

 Nautilicones have a persistent convex centran area in the impressed zone. No annular 

 known. ' , 



