VALVATID^. 213 



Geometriclae. As the animal proceeds, the rostrum and the small 

 foot are moved alternately. 



PALUDINELLA, Pfeiffer. Shell turbinated, oval or depressed, 

 umbilicated ; whorls rounded ; aperture subcircular, lip simple, 

 usually continuous. Amphibious, living in marshes usually near 

 the sea. A. littorea, Chiaje (Ixxiii, 18). 



ACMELLA, Blanford. Shell ovate, with a corneous epidermis ; 

 aperture ovate, the margin obtuse. Operculum corneous, thin, 

 paucispiral. Animal like Assiminea, with short proboscis, ten- 

 tacles short obtuse, with eyes on their sides, foot moderate, obtuse. 

 A. term, Benson (Ixxiii, 94). Damp places, Khasi hills, India. 

 A land rissoid allied to Assiminea. 



HYDROGEN A, Parreyss. (Georissa, Blanf.) Shell imperforated 

 or umbilicated, globosely turbinated ; aperture oval. Operculum 

 thin, corneous paucispiral. Dalmatia, India. Terrestrial. A. 

 Cattaroensis, Pfr. (Ixxiii, 95). 



LAGUNGULA, Bcusou, 1856. (Bcnsonia, Cantraine.) Shell tur- 

 binated, subglobular ; aperture oblong, large ; outer lip a little 

 reflected ; umbilicus profound, tortuous. A. pulchella, Benson. 

 Chusan. 



Family YALYATIDJE. 



Shell depressed conical or almost discoidal ; umbilicated ; 

 covered by a thin greenish epidermis. Operculum orbicular, 

 corneous, multispiral. 



Animal with a produced muzzle ; tentacles long and slender, 

 eyes at their outer bases ; foot bilobed in front ; branchial plume 

 long, pectinated, partially exserted on the right side, when the 

 animal is walking. Lingual teeth broad ; uncini 3, lanceolate ; 

 all hooked and denticulated (xi, 24). 



Yalvata, Miiller. 



Syn. — Yalvatinella, Betta. Cincinna, Hiibn. 



Distr. — Fresh water, mundane. V. piscinalis, Miill. (Ixxiii, 96). 



Shell depressed conical (in the typical group). Other charac- 

 ters, those of the family. 



The species are of small size, living in ponds and ditches and 

 slow-running water, principally in North America and Europe. 

 When the animal is moving, the delicate, retractile branchial 

 plume is projected over the neck. The female deposits her eggs 

 in a single, coriaceous, spherical capsule, which is affixed to 

 stones or the stems of aquatic plants. 



GYRORBis, Fitzinger. (Planorbitina, Betta. Planella, Schliit.) 

 Shell discoidal, depressed, widely umbilicated, whorls rounded. 

 Europe, America. V. cristata, Miiller (Ixxiii, 9*7). 



TROPiDiNA, H. and A. Adams. Shell turbinated, whorls 

 carinated. N. America. V. tricarinata, Saj^ (Ixxiii, 98, 99). 



