CHORISTOCERAS, HELICOCERAS, ETC. 223 



complete Ancylocerae ; the two genera/ should probably be 

 united. 



C. CRISTATUM, d'Orb. PI. 100. fig. 522. Clault. Southern 

 France. 



Genus CHORISTOCERAS, Hauer. 



Shell like Crioceras, but the lobes erenulated. 

 Four species. Upper Triassic. Austria. 



'Genus HELICOCERAS, <l'0rb. 



Shell spiral, siuistral ; whorls separate; annular costa* passing; 

 uninterruptedly over the siphonal side. 



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

 India, United States. 



Suhgenus Patoceras, Meek. 



Costa 1 interrupted on the siphon;) 1 side, leaving a narrow, 

 smooth space along the whole length of the s;nne. 

 H. TETLLEUXIT. d'Orb. PI. 101. fig. 529. Jurassic. 



Genus TURRILITES, Lam. 



Shell spiral, depressed to elongate, sinistral ordextral ; sutures 

 ix-lobed, foliated; aperture often irregular. 

 Thirty-seven species. Gault to Chalk. Europe. 



r elicoceras is distinguished from tliis genus by its separated 

 oi-ls. 



COSTATUS, d'Orb. PL 101, fig. 580. Chalk. 

 T. BOBLAYI. d'Orb. PL 101. fig. 531. 



Genus HETEROCERAS, d'Orb. 



ihell like Turrilites, but last chamber somewhat produced 



recurved. 



Five species. Cretaceous. Europe; United States. 

 H. EMERICTI. d'Orb. PL 101, fig. 5:52. 



Subgenus Helicancyloceras, Gabb. 

 Spire less elevated, volutions less decidedly in contact. 



