MOLLUSCA. 801 



Mem. 15; PFEIFPER Land- u. Wasserschn. i. Tab. iv. figs. 42, 43; STURM 

 Deutschl. Faun. vi. 2 ; BLAINV. Malacol. PI. 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, LEYDIG Ueber Palu- 

 dina vivipara, ein Beitrag zur ndhern Kenntniss dieses Thieres in embryo- 

 logischer, anatomischer und histologischer Beziehung, in SIEBOLD u. KOEL- 

 LIKER'S Zeitsch. f. wissench. Zool. n. 1850, pp. 125 197, PI. xi. xn. 



XIII.] 



Valvata MUELL. Shell discoiclal 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 piscinalix'FEimss., LAM., Cyclostoma oUusum DRAP., PFEIFFER 

 Land- u. Wasserschn. I. Tab. iv. fig. 32, STURM Deutschl. Fauna, vi. Heft 

 4, Tab. 2, BLAINV. Malacol. PI. 34, fig. 4, in fresh water, canals, &c. 



Cyclostoma LAM., DfiAPARN. 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 MUELL., BLAINV. Malacol. 

 PI. 34, fig. 7, PFEIFFER Land- u. Wasserschn. I. Tab. iv. figs. 30, 31, 

 GUERIN Iconogr., Moll. PI. 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 Pneumonica 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. J. 51 



