PULMOGASTROPODA. 



813 



Fig. 727. — Pupa (Dendropupa) 7>eUista 

 (after Dawson), a, Natural size ; b, En- 

 larged ; c, Apex enlarged ; d, Sculpture, 

 magnified. Coal-measures. 



is closed when the animal is withdrawn within it by a movable 

 calcareous plate ("clausilium"). A large number of recent species 

 of Clausilia are known, but the fossil 

 forms are not numerous, and the 

 oldest of them appear in the Eocene. 



In the genus Pupa the shell is 

 cylindrical or oblong, with a rounded, 

 often toothed aperture and a reflected 

 outer lip. The oldest known type 

 of this genus is the Pupa (Dendro- 

 pupa) vetusta of the Coal-measures 

 of Nova Scotia, discovered by Sir 

 William Dawson in the hollow trunk 

 of an erect Sigillaria. The aperture 

 in this form (fig. 727) is devoid of 

 teeth. An allied type is the Pupa 

 vermilione7isis of the Coal-measures 

 of the United States. With these 

 exceptions, the fossil Pupa are all 

 of Tertiary age. 



Lastly, in the genus Succinea the 

 shell is thin and ovate, with a small 



spire and a large body-whorl, the aperture large and obliquely 

 oval, and the outer lip thin. The " Amber-snails " live in moist 

 places on land, and the known fossil species are confined to the 

 Tertiary rocks. S. oblonga and ,5. putris are very common in the 

 Loess. 



Order II. Basommatophora. . 



In this order of Pulmonates the eyes are placed at the base of 

 two feelers, which are contractile, but are not capable of invagina- 

 tion. Of the families of this order, the Auriculidce. and Limn<zid<z 

 are inhabitants of fresh waters, or are amphibious, or in other cases 

 live in moist places on land, while the aberrant groups of the 

 Siphonariidce, and Gadi?iiidce are marine in habit. 



Family i. Auriculidce. — In this family the shell is spiral, with 

 a horny epidermis ; the aperture is elongated, generally with a 

 toothed outer lip ; and the columella is folded. The members of 

 this family inhabit salt-marshes and places overflowed by the sea. 

 The principal genus is Auricula itself, which ranges from the Upper 

 Jurassic rocks to the present day, but the fossil forms are of com- 

 paratively little importance. 



Family 2. Limn^eid^e. — In this family the shell is well developed, 

 thin and horn-coloured, and of very variable shape. The aperture 

 is simple, and the outer lip is sharp. The Limnceidce are all in- 



