SUB-ORDER B 



PLATYPODA 



AC,:} 



The \vi<l- 



i>mj>halopterus, Roem. Depressed turbinate, widely umbilicatt 

 pheral margin at the base composed of two lamellae, 

 separated by a slit. Silurian. 



Clisospira, Billings ; Autodetus, Lindstroiu. Silurian. 



Xenophora, Fischer (Phorus, Monti.), (Fig. 900). Low 

 trochiform, narrowly uinbilicate. Whorls usually covered 

 above with agglutinated extraneous objects. Cn-tan-mi.- t<> 

 Recent. 



Family 7. Ampullariidae. (!ra\. 



This family inhabits fivsh or brackish \\aln-. ;m>l ifl 

 found in Africa, Asia, and tropical America. Some of 

 their shells are hardly to be distinguished from Natica. 

 The animal possesses a lung cavity above the right gill. 

 Fossil forms occur in freshwater deposits of Cretaceous age at Rognac, near Marseilles, 

 and also in the early Tertiary. 



,., , MHI 



xenophora aggiutinans, Lam. 

 Growler; Dwwry, new 



Fia. 901. 



Valvata piscinalis, Mull. 

 Upper Miocene ; Vargas, 

 Transylvania. 



Family 8. Valvatidae. Gray. 



Shell composed of few whorls, conical or discoidal, umbilicate. Aperture round, with 

 continuous peristome. Operculum horny, circular, multispiral. 

 Upper Jura to Recent. 



The genus Valvata, Hull. (Fig. 901), is small, and varies 

 from turbinate to discoidal. It comprises about twenty-five 

 recent species, inhabiting the fresh waters of Europe and North 

 America. It is initiated in the Purbeck, but does not become 

 at all abundant until the Tertiary. 



Family 9. Viviparidae. Gill. 



Shell conical or turbinate, with thick epidermis; imperforate or with narrow 

 umbilicus. Whorls smooth, tubular or angular. Aperture rounded, oval, sub-angular 

 posteriorly, with continuous peristome. Operculum horny, concentrically striated, with 

 eccentric nucleus. Jura to Recent. 



Viviparus, Montf. (Paludina, Lam.), (Fig. 902). This, the principal genur-, i> 

 abundant in fresh water of all parts of the globe, with the exception of tropical and 

 South America. Several A B c Jf 



other genera and sub- 

 genera are recognised, 

 such as Campeloma, Raf. 

 (Melantho, auct.), of 

 North America, compris- 

 ing mostly smooth, thick - 

 shelled species, with 

 thickened inner lip; 

 Tulotoma, Haldem., in- 

 cluding forms with an- 

 gular whorls, North 

 America; Margarya, 

 Nev., China ; Lioplax, 

 Brusina, etc. 



Typical species of this genus are found in the Wealden clays. Vast numbers of 

 Viviparus occur in the Pliocene of Southern Hungary, Croatia, Slavonia, Roumania, 



FIG. 90-2. 



A, B, Viviparus Brusinae, Neumayr. C, V. (Tulotoma) Forbesi, Neumayr. 

 Pliocene ; Isle of Cos. D, V. (Tulotoma) Hocnuri, Neumayr. Pliocene , 

 Novska, Slavonia. 



Troschel ; Laguncula, Benson ; Tylopoma, Boskovicia r 



