MOLLUSCA. 801 
Mém. 15; Pruirrer Land- u. Wasserschn. 1. Tab. Iv. figs. 42, 43; STURM 
Deutschl. Faun. vi. 2; Buatnv. Malacol. Pl. 36, fig. 4; the shell is a dull- 
green, with red-brown bands and very convex wreaths. The right tentacle 
is perforated in the male individuals with an aperture which gives passage 
to the penis. The gills consist of three series of filaments. This snail, com- 
mon in fresh water, is viviparous, and the females are full of young in 
spring. It is found in Holland in canals and other fresh water, in the 
mud or hiding under stones, also creeping under water-plants, &c. [Con- 
sult especially, in addition to the works cited above, Leypta Ueber Palu- 
dina vivipara, ein Beitrag zur nihern Kenntniss dieses Thieres in embryo- 
logischer, anatomischer und histologischer Beziehung, in StEBOLD u. KOEL- 
LIKER'S Zeitsch. f. wissench, Zool. 1. 1850, pp. 125—197, Pl. Xi. XII. 
XII. | 
Valvata Murin. Shell discoidal or conical, with cylindrical 
wreaths. Aperture rotundate. Animal furnished with horny orbi- 
cular operculum, with foot anteriorly truncate or emarginate, with 
two slender tentacles, and with eyes sessile at the base of tentacles. 
Sp. Valvata piscinalis Firuss., Lam., Cyclostoma obtusum DRAP., PFEIFFER 
Land- u. Wasserschn. 1. Tab. ty. fig. 32, Srurm Deutschl. Fauna, vi. Heft 
4, Tab. 2, Buainv. Malacol. Pl. 34, fig. 4, in fresh water, canals, &c. 
Cyclostoma LAM., Draparn. Shell conical, short, with cylin- 
drical wreaths, the last ample, tumid. Aperture regular, rotund, 
with margins connected orbiculately, reflected by age. Animal 
with a thin orbicular operculum, two tentacles, and petiolate eyes 
at the base of tentacles. 
Sp. Cyclostoma elegans DRAPARN., Nerita elegans MvuEtu., Buarnv. Malacol. 
Pl. 34, fig. 7, Preirrer Land- wu. Wasserschn. 1. Tab. Iv. figs. 30, 31, 
GuERIN Iconogr., Moll. Pl. 12, fig. 12, &c. This genus also counts many 
fossil species from the tertiary formations. 
These animals differ from the rest of this family, inasmuch as they do 
not live in water, but in moist places, and breathe atmospheric air. Also 
they have a vascular net in place of gills, and on this account might 
belong to the following family, if the whole form of the body and the 
internal structure did not remove them from the Prewmonica and place 
them in the neighbourhood of Turbo. 
Helicina LAM. 
Ampullaria Lam. Shell globose, ventricose, umbilicate, with 
spire short, obtuse, sometimes discoidal. Aperture entire, oblong. 
Animal furnished with operculum, with long tentacles, and petiolate 
eyes at the base of tentacles. Respiratory cavity large, containing 
a pectinate branchia composed of a row of lamella, and a vascular 
pulmonary cavity. 
VOL, I. ol 
