CHORTSTOCERAS, HELICOCERAS, ETC. 223 



complete Ancylocerae ; the two genera sliould probably be 

 united. 



C. CEISTATUM, d'Orl). PI. 100. fig. 522. Uault. Southern 

 France. 



Genus CHORISTOCERAS, Hauer. 



Shell like Crioceras, but the lobes erenulated. 

 Four species. "Upper Triassict. Austria. 



Genus HELICOCERAS, d'Orb. 



Shell spiral, sinistral ; whorls separate; annular costffi passing 

 uninterruptedly over the siphonal side. 



Eleven species. Inferior Oolitic (?) to Cretaceous. Europe, 

 India, United States. 



Subgenus Patoceras, Meek. 



Costse interrupted on the siphonal side, leaving a narrow, 

 smooth space, along the whole length of the same. 

 H. TEILLEUXIT, d'Orl). PL 101, fig. 529. Jurassic. 



Genus TURRILITES, Lam. 



Shell spiral, depressed to elongate, sinistral or dextral ; sutures 

 six-lobed, foliated ; aperture often irregular. 



Thirty-seven species. Gault to Chalk. Europe. 



Helicoceras is distinguished from this genus by its separated 

 whorls. 



T. COSTATUS. d'Orb. PI. 101, fig. 530. Chalk. 

 T. BOBLAYI, d'Orb. PI. 101, fig. 531. 



Genus HETEROCERAS, d'Orb. 



Shell like Turrilites, but last chamber somewhat produced 

 and recurved. 



Five species. Cretaceous. Europe; United States. 

 H. EMERICII, d'Orb. PI. 101, fig. 5:5-2. 



Subgenus Helicanoyloceras, Gabb. 

 Spire less elevated, volutions less decidedly in contact. 



