122 systematic arrangement 



1. Vanicoro. 

 Character of the Family. 



1. V. Souleyetana, t. 128. f. 1. 



2. V. cancellata, t. 103. f. 3. 



3. V. Deshayesiana, Beclus, Mag. Zool. 1845, t. 130. f. 20. 



The body of V. cancellata spiral. Trunk proboscis-like. Ten- 

 tacles conical, simple, with the eyes on their outer bases. The foot 

 is small, rounded, with an oblong expansion in front ; a large trian- 

 gular wing-like lobe on each side. The edge of the mantle is simple. 

 The operculum very small, thin, just at the top of the foot. 



Foot formed of two parts, separated by a deep cross groove ; the an- 

 terior very extensible, rounded in front and double-edged, truncated 

 behind; the hinder portion smaller, rounded like a sucking disk, 

 with a membranaceous expansion on each side, angularly produced 

 in front. The operculum is placed behind and above the lateral 

 lobes. Gills oblique, on the left side, and formed of a single series 

 of triangular, partly free plates. Mantle edge simple, without any 

 trace of siphon or membranaceous appendage. 



e. Gills plumose, pinnate, exsertile, laminar, spiral, twisted 

 (pp. 78, 86, 95, 115). 



Fam. XXIII. VALVATIDiE. 



Gills plumose, exserted ; laminae pinnate, spirally twisted. Ros- 

 trum produced, short, prominent, truncated ; the mouth terminal. 

 Tentacles subulate. Operculum orbicular, spiral, of many whorls. 

 Shell conic or discoidal. Periostraca thin, olive. Mouth round. 

 Peristome continuous. 



Fluviatile. 



1. Valvata. 

 Shell conic or discoidal, umbilicated. 



1. V. cristata, t. 6. f. 3, 1. 126. f. 1, 1. 126 a. f. 6 ; Forbes fyHanley, 



B.M. t. H.H. f. 5 ; Adams, Gen. Moll. t. 36. f. 6. 



2. V. planorbis, t. 126. f. 2. 



Fig. 63. — Teeth of Valvata piseinalis. 



The lingual plate of Valvata piseinalis is elongate ; the central 

 tooth subquadrate, base produced on both sides, incurved ; cutting 

 edge triangular, the middle cusp with a pectinated lobe on each 



