CLASS IV 



GASTEOPODA 



547 



Subgenera ; 

 Recent. 



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



Siliquaria Bnig. (Fig. 965). Shell 

 free, coiled in a loose spiral. Aperture 

 lateral, and with a slit which continues 

 as a fine cleft or row of pores through- 

 out the entire length of the shell. 

 Cretaceous to Recent. 



963. 



Vcrmicidaria (Th yhwode-i) arenaria 

 Linn. Miocene ; Grund, near Vienna. 

 Vs. 



V. (Petaloconchus) intorta Lam. 

 Pliocene ; Montespertoli, near 

 Florence. Some of the tubes are 

 fractured i and show the internal 

 lamellae. 



Fir;. 965. 



Siliquaria striata 



Desh. Calcaire Grossier ; 

 Chaussy, near Paris. 



Family 14. Caecidae Adams. 



Shell small, discoidal in early stages, later becoming tubular. The decollated yroto- 

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

 Recent. 



Caecum Flem. About 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 brackish, 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 I'ounded. Upper Jiira to Recent. 



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

 verse ribs ; aperture rounded, with entire, thickened and reflected 

 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 



Fig. 966. 



Melania escheri 

 Brongt. Miocene ; 

 Michelsberg, near 

 Ulni. 



