CLASS IV 



GASTROPODA 



543 



present, often partially or entirely filled with callus. Aperture semicircular or oval. 

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



Trias onward. 



Subgenera : Ampullina Lam. (Fig. 944) ; 

 Amauro2)sis Morch. (Figs. 945, 946) ; Polinices 

 Montlbrt ; Euspira Agassiz ; Lunatia, Cernina 

 Gray ; Neverita Risso, etc. 



(?) Deshayesia Raul. 

 (Fig. 947). Lil^eNatica, 

 but inner lip with a 

 thick callus and den- 

 ticulated. Miocene and 

 Pliocene. 



Fio. 945. 



Nntiai, {AmpulHna) 

 wilhmeti. Lam. Cal- 

 caire Grossier ; Da- 

 mery, near Epernay. 



Fig. 946. Fio. 947. 



Natica (Amauropsls) Deshayrsia cochlearia 



hnlhi/ormis Sowh. Upper (Brongniart). Oligocene; 



Cretaceous; St. Gilgen Monte Grnmi, near 



on Wolfgangsee, Austria. Vicenza. 



Family 6. 

 Xenophoridae 



Deshayes. 



Shell turbinate, with- 



ut nacreous layer ; 

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

 a peripheral heel. Aperture obliquely quadrilateral. Operculum horny. Silurian to 

 Recent. 



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

 have acquired a high diiferentiation. 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. 



Clisosinra Billings ; Autodetus 

 Lindstrom. Silurian. 



Xenophora Fischer {Phorus 

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



Fiii. 948. 



Eotrochus heliacus 

 (d'Orb.). Upper Lias ; La 

 Verpilliere, near Lyons. 



Fig. 949. 



Xenophora ngglutinans (Lam.). 

 Calcaire Grossier ; Damery, near 

 Epernay. 



Whorls usuallv covered 



above with agglutinated extraneous objects. 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- 

 Una. The animal possesses a lung cavity above the right gill. Fossil forms occur in 

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

 Tertiary. 



