CLASS V 



CEPHALOPODA 



605 



Annular lobes absent except in a few Triassic forms. SifMmcle 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 



Hercoceras mirnm Barr. 



Piri. 1120. 



Devonian (Etage G) ; Hlubocep, Bohemia 

 (after Barrande). 



Fli:. 11-21. 



rtenoeernt' (Gyr.) alatiim 

 (Ban-.). Silurian (F) ; 

 Konieprus, Boh( 

 (after Banande). 



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

 less spout-like processes. Suttires with ventral, lateral and dorsal lobes. 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 

 Ihrotighout life are trapezoidal in section, tuberculated, and without well-defined lateral 

 and umbilical zones. Sutures have ventral, lateral and dorsal, but no annular lobes. 

 Spiinous processes are complete, never spout-lihe. Siphuncle small, tubular. 



Temnocheilus M'Coy {Endolobus Meek and Worth ; Cryptoceras 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 Goelogasteroceras Hyatt. Carboni- 

 ferous. Biadiploceras Hyatt. Devonian. Tainoceras Hyatt. Carboniferous. 



Family 19. Oentroceratidae Hyatt. 



Gyroceracones and nautilicones with young similar to early stages of Temnocheilus 

 btfore the impressed zone is formed. Shell subsequently becoming 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 

 lobes knoivn. 



