654 



MOLLUSCA 



PHYLUM VI 



choceras Gabb 



Fig. 1258. 



A, Baculites anceps Lam. B, B. faujasi 

 Lam. Upper Cretaceous ; Maestricht. t 



Fig. 1259. 



Suture-line of Diplomoceras cylindraceum 

 Defr. Uppermost Cretaceous ; Tresville, 

 Manche. 



Oyrtochilus Meek {Scipionoceras Hyatt) ; Baculites Lam. (Fig. 1258). 



Diplomoceras Hyatt (Fig. 



1259). Type D. (Harn.) cylin- 



ß draceum, (d'Orb.). Hamulina 



d'Orb. (Fig. 1260, A). Cre- 

 taceous. Baculina d'Orb. 

 Juras. 



Subfamily C. Turrilitinae 

 Hyatt {pars). 



A heterogeneous group 

 of turret-shaped cones, with 

 Shells highly ornamented 

 witb ribs and tubercles. In 

 Turrilites the spire is sym- 

 metrical and close-coiled ; in 

 most other forms it is un- 

 symmetrical, and niore or less 

 open. The relationship of 

 this group to the Lytocera- 

 tidae is extremely problema- 

 tical. 



Turrilites Lamarck. (Fig. 

 1261); Heteroceras d'Orb. 

 (Fig. 1262); Emperoceras 

 Hyatt ; Helicoceras d'Orb. 

 Cretaceous. 



Fig. 1260. 



A, Hamulina subcylin- 

 drica (d'Orb.). B, Suture- 

 line of A. lorioli (Uhlig). 

 Neocomian ; Angles, Basses 

 Alpes (after Uhlig). 



Family 21. Aegoceratidae Neumayr. 



Form discoidal, mostly widely umbilicate. Whorls 

 smooth, or with straight radial rihs that occasionally 

 hifurcate at the venter. Aper- 

 ture without lateral ears. 

 Venter with keel, or with for- 

 ward pointing crest. Body 

 Chamber comprising from 

 three-fourths to more thart, a 

 complete revolution. Suture 

 line not deeply digitale ; 

 usually with only two lateral 

 lobes and an auxiliary. 



Subfamily A. Psilocera- 

 TiNAE Zittel. 



Widely umbilicate, 

 whorls laterally compressed, 

 smooth or with simple ribs 

 whicli do not cross tlie fig. 1261. 



rounded keelless venter. 



The Psiloceratinae are 



Fig. 1262. 



GlnU^viiZJV''''''^''' "^'P""^- Heteroceras polyplomim (Roemer). 

 d'Orbigny). ' """ ^ Upper Cretaceouf ; Haldem, West- 



