244 



THE LIAS AMMONITES. 



curvature receives many modifications, and exists in some of the examples in more than 

 one plane, are all suppressed, and the whole series is reduced to the single genus Hamites, 

 which, in the primary significance of the word, implied a conical straight shell, as 

 Hamites elegans, d'Orb, (fig. 142), bent in one plane, without the bends being in 



Fig. \i2.~— Hamites elegans, d'Orb. 



contact. The suture-line is divided into six lobes ; the upper lateral lobe always, the under 

 lateral mostly, divided into pairs of branches. 



Genus Turrilites, Lamarck. — Under this genus Professor Neumayr classes Helico- 

 ceras (fig. 143), with an open spiral not in one plane, and Heteroceras, with a closed 

 spiral only in the earlier stage of growth. In Turrilites (fig. 143) the suture-line is 



Fig. 143. — Turrilites caienatus, d'Orb. Fig. 144. — Helicoceras Eolertsoni, d'Orb. 



divided into six lobes, each formed of a single pair of digitations. The ventral lobe 

 formed of a pair which are a little longer or shorter than the lateral. 



Gemis Baoulites, Lamarck. — This genus connects, according to Professor Neumayr, 

 Lytoceras with Hamites in the structure of the principal lateral lobe. Baculites 

 (fig. 145) has a straight conical shell. Mouth oval or compressed, provided on the ventral 



Fig. 145. — Baculites anceps, Lamarck. 



