CLASS IV 



GASTROPODA 



545 



Staliola Brusina. Outer lip thickened ; operculum calcareous. Cretaceous to 

 Miocene. 

 A (• Fossarulus Neumayr. Like the last, but witli spiral ribs. 



Upper Miocene. 



Nematura Benson (Stenothyi-a Benson) (Fig. 953). Like 

 Bithinia, but aperture contracted. Operculum calcareous, spiral. 

 Tertiary and Recent. 



Fig. 952. 



A, Bithinia tentaenlata 

 (Linn.). Upper Mionene; 

 Miocic, Dalmatia. B, 

 Operculum of same. C, 

 B. grariUs Sandb. Fresh- 

 water JVIolasse ; Uber- 

 kirchberg, near Ulni. 



Pig. 953. 



Nematura pupa (Xy.st). 

 Oligocene ; Hackenlieim, 

 near Alzey. 



Fig. 954. 



Nystia chastelii 

 (Nyst). Middle Oligo- 

 cene ; Klein-Spouwen, 

 Belgium. 



Fig. 955. 



Hydrobia acuta A. 

 Braun. Miocene ; 

 Weissenau, near 

 Mayence. 



Nystia Tourn. (Forbesia Nyst) (Fig. 954). Outer lip reflected; operculum 

 calcareous, spiral. Tertiary and Recent. 



Assiminea Leach. Tertiary and Recent. 



Hydrohia Hartm. (Littorinella Braun ; Tournoueria Brusina) (Fig. 955). Conical 

 to turreted, acuminate, smooth. Aperture oval ; operculum horny, paucispiral. 

 Cretaceous to Recent. The Indusia Limestone (Lower Miocene) of Axivergne is 

 almost exclusively composed of the shells of H. dubuissoni Bouill. Similarly, the 

 Littorinella Limestone ,of the Mayence Basin, which is of equivalent age, is made 

 up of the shells of H. acuta Braun. Strata in the fresh-water limestone of Nordlingen 

 are charged with H. frochulus Sandlj. ; and the Upper Eocene marl of St. Ouen is 

 filled with the remains of H. pusilla (Prev.). 



Other genera and subgenera closely related to the foregoing are Bythinella Moq. ; 

 Amnicola Gould ; Belgrandia and . j, ^, 



Lartetia Bourguignat ; Lapparentia 

 Bertlielin. 



Pyrcjula Christofori and Jan. 

 (Fig. 956, A). Turreted, whorls 

 spirally keeled or ribbed. Peristome 

 continuous. Tertiary and Recent. 



Genera allied to the last are 

 Micromelania Brus. (Fig. 956, B) ; 

 Mohrensternia Stol. (Fig. 956, C) ; 

 Pyrgidium Tournouer ; Prnsosthenia 

 Neumayr. Tertiary. 



Lithoylyphns Ziegl. (Fig. 957). 

 Globose or ovate, with short sj)ire ; 

 rather thick and solid. Aperture large, obliquely oval ; inner lip thickened. 

 Tertiary and Recent ; Europe. Similar forms, Somatogyrus Gill, and Flmnincola 

 Stirapson, occur in North America. There are other related genera in south-eastern 

 Asia and South America. 



Family 11. Rissoidae Troschel. 



Shell small, thick, turbinate to turreted, usually ribbed or spirally striated, rarely 

 smooth. Aperture oval, angular posteriorly, often with anterior canal. Operculum 

 horny, pavjcispiral. Jura to Recent. 



Rissoina d'Orb. (Fig. 958). Turreted, transversely ribbed, rarely smooth : outer 

 VOL. I 2 N 



Fig. 95(3. 



A, Pyrcjula eugeiiiae Neumayr. 

 Upper Miocene ; Arpatak, Transyl- 

 vania. B, Micromelania {Diana) 

 haueri (Neumayr). Upper Miocene ; 

 Miocic, Dalmatia. C, Mohrensternia 

 inflata Andrzewsky. Congerien Stage 

 (Miocene) ; Inzersdorf, near Vienna. 



Fig. 957. 



Litho<jJyphiiii fuscus 

 Ziegler. Upper Mio- 

 cene ; Malino, West 

 Slavonia. 



