586 MOLLUSCA SUB-KINGDOM VI 
and Camp.; Lyticoceras, gen. nov. (Fig. 1225). Type L. (Amm.) eryptoceras, d’Orb. sp. ; 
(?) Vascoceras, Choff.! Cretaceous. 
Family 26. Hamitidae. A provisional group of uncoiled shells having single 
costae crossing the venter uninterruptedly, and no tubercles at any stage. 
Hamites, Park. ; Hemibaculites, gen, nov. Type H. (Toxoc.) obliquatum, VOrb. sp. ; 
Dirrymoceras, gen. nov. Type D. (Ancyl.) simplex, VOrb. sp.; Torneutoceras, gen. nov. 
t} 

Fic. 1226. 
Fic. 1225 
. Torneutoceras rotundatum, 
Lyticoceras Noricum, Sowb. sp. (=Hoplites amblygonius, Neuna.). Sowb. sp. Gault; Folke- 
Neocomian ; Achim, near Borsum, Prussia. stone. 
(Fig. 1226). Type 7. (Ham.) attenuatus, VOrb. sp. Possibly here also should be 
placed Helicoceras and Heteroceras, VOrb.; and Lindigia, Karstens—all asymmetrical 
spirals, but im old age forming a secondary crook striking off from the spire. 
Cretaceous. 
X. COSMOCERATIDA, 
Highly tuberculated and costated forms having a smooth zone on the venter or costae 
extending across it, but never with a line of median ventran tubercles nor a keel at any 
stage. Numerous phylogerontic uncotled forms occur in the Cretaceous. 
Family 27. Cosmoceratidae. Discoidal and involute forms having at a 
comparatively early stage or throughout life two or three rows of large tubercles 
on each side, and costae interrupted on the venter by a smooth median zone or 
channel. 
Late stages of all genera except Cosmoceras and Phricodoceras have costae continuous 
across the flattened venter, and species of the latter indicate possible transitions to 
Aimblycoceras. All forms have a Cosmoceran stage quite distinct from the young of 
Morphoceratidae. 

' P. Choffat, Receuil d'études paléontologiques sur la faune crétacique du Portugal, Les 
Ammonees du Bellasien, ete. Lisbonne, 1898. 
