GASTROPODA 



543 



jiresent, often iiartially or entirely filled witli calliis. Aperture semicircular or oval. 

 Outer lip sliaip ; inner lip thickened by a callus. Excessively abundant from the 



Trias onward. 



Subgenera : Ampullina Lam. (Fig. 944) ; 

 Amaurojysis Mörch. (Figs. 945, 946) ; Polinices 

 Montfort ; Euspira Agassiz ; Lunatia, Cernina 

 Gray ; Neverita Risso, etc. 



(?) Deshayesia Raul. 

 (Fig. 947). Like Natica, 

 but inner lip witb a 

 thick callus and den- 

 ticulated. Miocene and 

 Pliocene. 



Family 6. 



Xenophoridae 



Deshayes. 



Shell turbinate^ with- 

 out nacreous layer ; 

 whorls flat, often covered with agglutinated foreign hodies. Base concave or flat, with 

 a peripheral keel. Aperture ohliquely quadrilateral. Operculum horny. Silurian to 

 Recent. 



Fig. 945. 



Natiai {Ampullina) 

 loülemetl Lam. Cal- 

 caire Grossier; Da- 

 mery, near Epernay. 



Fig. 946 



Natica (Amauropsis) 

 biilbiformis Sowh. Upper 

 Cretaceous ; St. Gilgen 

 on Wolfgangsee, Austria. 



Deslutyesia cochUaria 

 (Brongniart). Oligocene ; 

 Monte Grumi, near 

 Vicenza. 



The Xenophoridae are an ancient family, the modern representatives of which 

 have acquired a high differentiation. The radula is like that of the Capulidae, 

 Littorinidae and Strombidae, not like that of the Trochidae. The earlier forms, 

 encountered in the Silurian, present a great superficial resemblance to the Paleozoic 

 Trochus species, 



Eotrochus Whitfield (Fig. 948). Thin-shelled, turbinate, widely umbilicate. 

 Whorls flat, rarely with aggluti- 

 nated foreign particles. Base con- 

 cave, its periphery formed by a 

 compressed lamellar belt. Silurian 

 to Recent. 



Omphalopterus Roemer. De- 

 pressed turbinate, widely umbili- 

 cate. The wide peripheral margin 

 at the base composed of two lamellae, 

 separated by a slit. Silurian. 



Glisospira Billings ; Autodetus 

 Lindström. Silurian. 



Xenophora Fischer {Phorus 

 Montf.) (Fig. 949). Low trochiform, narrowiy umbilicate. 



Fig. 949. 



Eotrochus heliacus 

 (d'Orb.). Upper Lias ; La 

 Verpilliere, near Lyons. 



Xenopliora agglutinans (Lam.). 

 Calcaire Grossier ; Damery, near 

 Epernay, 



Whorls usuallv covered 



above with agglutinated extraneous objeots. Cretaceous to Recent. 



Family 7. Ampullariidae Gray. 



This family inhabits fresh or brackish water, and is found in Africa, Asia and 

 tropical America. Some of their shells are hardly to be distinguished from Ampul- 

 lina. The animal possesses a lung cavity above the riglit gill. Fossil forms occur in 

 fresh -water deposits of Cretaceous age at Rognac, near Marseilles, and also in the early 

 Tertiary. 



