PLATE I. 



Psil. planorbe. Fig. 1, cast with incomplete living chamber, showing folds at an early- 

 stage of growth. Fig. 2, suture much enlarged. Loc. Whitby. Fig. 3, 4,, cast with similar 

 folds in the young, but smooth in the adult. Fig. 4 a. young of Fig. 4 enlarged. Loc. Neuffen. 

 Fig. 5, 6, cast of the more involute variety, loc. Balingen. The specimen has distorted sutures, 

 showing the broad abdominal lobe and the large median saddle on one side, but is otherwise 

 normally formed. 



Cal. Nodotianum. Fig. 7, 1 specimen reduced to less than one half, showing incomplete 

 living chamber. Fig. 8, sutures enlarged. Fig. 9, a fragment of a cast showing sutures and 

 part of living chamber. Fig. 10, section of four whorls. Fig. 11, a cast. Fig. 11 a, section of 

 last whorl. Loc. Semur. 



Cal. tortile. Fig. 12, specimen with portion of living chamber. Fig. 13, same, portions 

 of the two outer whorls removed, showing their rounder outlines. Fig. 14, suture of same, 

 enlarged. Loc. Semur. 



Cal. carusense. 2 Fig. 15, cast of the younger stages, broken out of the interior of an 

 adult specimen, loc. Balingen. Fig. 16, cast, loc. St. Thibault. 



"Verm, spiratissimum. Fig. 17, cast, living chamber incomplete, loc. Nellingen. Fig. 18, 

 specimen with distinct channels, developed at an early age, loc. Semur. 



Cal. sulcatum. Fig. 19, specimen with incomplete living chamber, showing the smooth 

 young in the centre. Fig. 20, suture of the same, enlarged. Loc. Semur. 



Verm, ophioides. Fig. 21, cast of a broken specimen, showing the well developed chan- 

 nels and keel in the young, and the early appearance of the pilse. Figs. 22, 23, sutures of this 

 and au older specimen, enlarged. Loc. Semur. 



Cal. raricostatum. Fig. 24, specimen, showing the senile metamorphoses. Fig. 25, 

 section of last two whorls, showing the corresponding change of form for comparison with 

 Fig. 25 a, the adult of the same variety. 3 Loc. Balingen. 



1 This figure is not numbered. 2 See Plate II. Fig. 1. 



3 See Plate VI. Fig. 15, for the Johnstoni-like variety. 



