200 THE LIAS AMMONITES. 



Septa symmetrical, divided into unequal lobes. Mouth, round or oval, and provided 

 with tubercles at the circumference. Siphuncle marginal. This genus ranges from the 

 Inferior Oolite to the upper strata of the Chalk, and Ancyloceras Mather onianum, d'Orb. 

 (fig. 89), from the Upper Neocomian, and Ancyloceras Puzosianum, d'Orb. (fig. 90), 

 from the lower Neocomian, are typical of the genus. 



Fig. 90. — Ancyloceras Puzosianum, d'Orb. 



i. Species only arched. 



Genus Toxocekas, d' Orhigny. Shell conical, subcylindrical or compressed, symme- 

 trical, much elongated, and more or less arched, but never forming a spire. Septa 

 transverse, deep, sinuous, and presenting six unequal lobes, foliaceous on their border. 

 Siphuncle marginal. Mouth oval, compressed or round, prominent at the inner border. 

 The species belong to the Jurassic and Cretaceous formations. Toxoceras Honnora- 

 tianum, d'Orb. (fig. 91), is typical of the group. 



Fig. 91. — Toxoceras Honnoratianum, d'Orb. 



Genus, Hamites, Parkinson. Shell conical, symmetrical, bent upon one plane, 

 spire irregular, very elliptical, formed of bends at the two extremities of the ellipse. 



Fig. 92. — Hamites elegans, d'Orb. 



