MANUAL OF THE MOLLUSCA. 



6. Ceratttes (see p. 197). 



Division II. — Sutures foliated 



Including the genera Ammonites (p. 197), Toxoceras, Ancylo- 

 ceras* Scaphites, Helicoceras, and Turrilites (p. 200), Hamites, 

 Ptychoceras, and Baculites (p. 201), and the following. 



Antsoceras (see p. 200), Pictet, 1854. 



Etymology, anisos, unequal ; and ceras. 



Example, Hamites armatus, Sowerby. 



Shell at first growing in an open helicoid spire, afterwards 

 more or less prolonged and reflected; ornamented by trans- 

 verse ribs. Sutures of septa divided into 5 lobes and 5 saddles, 

 all bipartite ; the lateral saddles are the largest. 



Fossil, 12 species. Gault — Upper Green Sand, Europe. Cre- 

 taceous, India. 1 species, Jurassic. North-west Himalayas. 



Species of Belioceras founded on helicoid portions of shells 

 may belong to this genus. 



TTamulina (see p. 201), D'Orbigny, 1852. 



Example, H. dissimilis, D'Orb. 



Shell conical prolonged, having a portion of the body chamber 

 reflected, but not touching the other portion ; section of the 

 shell round or laterally compressed ; sutures of the septa 

 divided into six lobes, and as many saddles. 



Hamulina differs from Hamites in being only once reflected 

 instead of twice, and from Ptychoceras in having the reflected 

 portion of the shell separate from the other, not close together. 



Distribution, 15 species. Neocomian, France. Ootatoor 

 group (= ? Gault), India. 



Peltarion, Deslongchamps, 1859. 



Founded on the mandibular armature of tetrabranchiate 

 cephalopods 



* Many of the forms considered to belong to Crioceras have been ascertained 

 by M. Astier to be only more or less incomplete individuals of species belonging to 

 Ancyloceras. That Crioceras must merge into Ancyloceras appears inevitable. 



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