CLASS IV 



GASTROPODA 



.47 



Subgenera : Thylaeodes Guettard (Fig. 963) ; Petaloconchus Lea (Fig. 964). Tertiary and 

 Recent. 



Siliquaria Brug. (Fig. 965). Shell 

 free, coiled in a loose spiral. Aperture 

 lateral, and with a slit whicli continues 

 as a fine cleft or row of pores tlirougli- 

 out the entire length of tlie shell. 

 Cretaceous to Recent. 



Fig. 963. 



Vermicularia {Th ylacodes) arenaria 

 Linn. Miocene ; Grund, near Vienna. 



V2. 



V. (Petaloconchus) intorta Lam. 

 Pliocene ; Montespertoli, near 

 Florence. Some of the tubes are 

 fractured i and show the internal 

 lamellae. 



Fig. 965. 



Siliquaria striata 



Desh. Calcaire Grossier ; 

 Chaussy, near Paris. 



Family 14. Oaecidae Adams. 



Shell small, discoidal in early stages, later becoming tubulär. TJie decollated yroto- 

 conch replaced by a septum. Operculum round, horny. Tertiary and 

 Recent. 



Gaecum Flem. Abont one hundred Recent and twenty Tertiary 

 species are known. 



Family 15. Melaniidae (Lamarck) Gray. 



Shell turreted to oval, with thick, dark-coloured epidermis. Apex 

 usually truncated and corroded. Aperture oval, sometimes canali- 

 culate. Operculum horny, spiral. Jura to Recent. 



Living species inhabit fresh, or more rarely brackisli, waters of 

 Southern Europe and the warmer zones of Africa, Asia and America. 



Melania Lam. {Thiara Bolten) (Fig. 966). Shell smooth or 

 spirally striated, or with transverse ribs or nodes. Aperture oval, 

 anteriorly rounded. Upper Jura to Recent. 



Stomatopsis Stäche. Whorls platform-like, with strong trans- 

 verse ribs ; aperture rounded, with entire, thickened and reflected uim!^ ^ ^^^ 

 margins. Lowermost Eocene (Cosina Beds) ; Istria and Dalmatia. 



Pyrgulifera Meek (Hautkenia Munier-Chalm.) (Fig. 967). Shell thick, elongate- 

 oval, with platform-like, transversely ribbed, and spirally striated whorls. Aperture 



Fio. 966. 

 Melania eseheri 



Brongt. 



Miocene ; 

 near 



