654 



MOLLUSCA 



PHYLUM VI 



choceras Gabb ; Cyrtochilus Meek 



Fi(!. 1258. 



A, Baculites anccpx Lam. B, B. faiijasi 

 Lam. Upper Cretaceous ; Maestricht. I 



Fig. 1259. 



Suture-line of Diplomocerascylindraeeum 

 Defr. Uppermost Cretaceous ; Tresville, 

 Manclie. 



(Sci^nonoceras Hyatt); Baculites Lam. (Fig. 1258). 



Diplomoceras Hyatt (Fig. 

 1259). Tyi^e D. (Ham.) cylin- 

 draceum (d'Orb.). Hamulina 

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

 taceous. Baculina d'Orb. 

 Jiiras. 



Subfamily C. Turrilitinae 

 Hyatt {pars). 



A heterogeneous group 

 of turret-shaped cones, with 

 shells highly ornamented 

 with ribs and tubercles. In 

 Turrilites the spire is sym- 

 metrical and close-coiled ; in 

 most other forms it is un- 

 symmetrical, and more 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); Eviperoceras 

 Hyatt ; Helicoceras d'Orb. 

 Cretaceous. 



Fic. 12(50. 



A, Hamulina suhcylhi- 

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

 line of A. lorioU (Uhlig). 

 Neocouiiaii ; Angles, Basses 

 Alpes (after Uhlig). 



Family 21. Aegoceratidae Neumayr. 



For7n discoidal, mostly widely u'liibilicate. IVhorls 

 smooth, or with straight radial ribs that occasionally 

 bifurcate at the venter. Aper- 

 ture xoithout lateral ears. 

 Venter with keel, or with for- 

 ward pointing crest. Body 

 chamber comprising from 

 three-foiirths to more than a 

 complete revolution. Suture 

 line not deeply digitate; 

 usually with only two lateral 

 lobes and an auxiliary. 



Subfamily A. Psilocera- 

 TINAE Zittel. 



Widely umbilicate, 

 whorls laterally compressed, 

 smooth or with simple ribs 

 which do not cross the 

 rounded keelless venter. 



Fig. 12G2. 



Fig. 1261. 



Tnrrilitrs catenntna d'Orb. Heteroceras polyjilocum (HoeTneT). 



„, T^ -1 .■ Gault ; Escragnolles, France (after Upper Cri'taceous ; Haldeni, West- 



The Psiloceratmae are d'Orbigny). piiaiia. 



