WOOD, PHYLOGENY OF CERTAIN CERITHIID^ 79 



The development of this shell, as well as its adult ornamentation, has 

 all the characteristics of Yulgoceritliium. It resembles V. minitum to 

 su3h an extent that it was at first thought to be the young of that species, 

 but it is more accelerated than T'. miniitum. acquiring its tertiary spirals 

 at an early stage. It differs further from the latter species in having a 

 narrower aperture and longer canal. The well-developed callus and 

 nearly uniform size of all of the ten individuals studied seem to indicate 

 that the specimens are fully adult. 



F. CRETACIC SPECIES OF CERITHIUM 



No actual specimens of true Cerithium from horizons earlier than the 

 Aptien were available for study, and the following phylogeny worked out 

 from the literature is subject to revision, if more material should be 

 -obtained. 



Cerithium cornuelianum d'Orbigny 



1842-1843. Cerithium cnrnueJianum d'Orbign.y. Paleontol. FrariQaise, Terrains 



Cretaces, II, Gasteropodes, p. 3fil, pi. 228. figs. 11-13. 

 1906. Atresius cornuelianum Cossmann. Essais de Paleoconch. Comp., VII, 195. 



The original description is as follows : 



Dimensions : Ouverture de Tangle spiral, 27° ; longeur totale. 27 milliin. ; 

 lai-geur. 12 millim. ; longeur du dernier tour, par rapport a I'ensemble 35/100 ; 

 angle sutural, 89°. 



Coquille allongee, turriculee. Spire formee d'uu angle regulier, composge 

 de tours convexes, ornes en travers, a la derniere revolution spirale, de dix 

 cotes flexuenses. ondulees, non arretees, se correspondant obliquement d'un 

 tour k I'autre. Sur ses cotes viennent se croiser de l§gers sillons longitudi- 

 naux tres-inegaux. Bouche ovale, prolongee en avant et terminee par un 

 sinus; labre tres-echanere en arriere, saillant anterieurement. 



Horizon and locality : Aptien. Grange-au-Ru, near the Varin bridge, com- 

 mune de Wassy (Haute Marne). 



Eemarks : This species has volutions of a rounded outline, ribs con- 

 tinuous across the whorl and numerous spirals of different orders. It is 

 thus a simple shell, having the characteristics which might be expected 

 in an early type of true Cerithium. A specimen in the Museum of Com- 

 parative Zoology does not show the young stages, but on the last three 

 volutions two of the spirals are stronger than the others. This suggests 

 the beginning of the development which becomes a characteristic feature 

 of Cerithium (pquispirale and later species of the genus. 



A posterior tooth is not developed on the inner lip, but this would 

 hardly be expected before the spirals have become strong on the body 



