CHORTSTOOEKAS. HKI,I('0("KK AS, K/m. 223 



(•<)m|)l('tc Aiicylocci'ie ; llic two gc'iuM':! slioiild prohiilil V In- 

 imited. 



C. CRiSTAiniM. (I'Oi'l). I'l. 100. lio-. r>22. (iaull. Soullnrni 

 France. 



Genus CHORISTOCERAS, Haiier. 



Shell like Crioceras, but the lobes creniUated. 

 FowY species. Tipper Ti'ias.sic. Austria. 



Genus HELICOCERAS, (rOrb. 



Shell spiral, sinistral ; whorls separate; aiiiiiilar costa- i)assiiig- 

 uninterruptedly over the siphonal side. 



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

 India, United States. 



Subgenus Patoceras, Meek. 



Cost^e interrupted on the siphonal side, leaving a uari-ow, 

 smooth space along the whole length of the same. 

 H. Teilleuxii, d'Orb. 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. Ganlt 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 chanilier somewhat i)roduced 

 and recurved. 



Five species. Cretaceous. Europe; United States 

 H. Emertctt, d'Orb. PI. 101, fig. 532. 



Subgenus Helicancyloceras, (iabb. ' ~<L*v 



Spire less elevated, volutions less decidedly in contact.^ . , i^ fij A R YJ uoj 



