PLATE VI. 



Cor. Gmuendense. Fig. 1, 2, figures reduced to about one third, taken from a specimen 

 which exhibited compressed whorls and convergent sides at an older stage than in the specimens 

 figured on Plate V. Old age is apparent also in the two closely approximated sutures of outer 

 whorl. Loc. Aalen. 



Cor. trigonatum. 1 Fig. 3, large variety, having stouter and more numerous whorls, and 

 arriving at the same stage of senile decline later than in the smaller variety described in the 

 text, figure reduced to about one third. Loc. Aalen. 



Cor. Sauzeanum. 2 Fig. 4, young, loc. Whitby. Fig. 5, another older specimen, loc. 

 Semur. Fig. 6, another specimen, broken across, showing embryo, and having keel just begin- 

 ning to be perceptible on the outer whorl. Fig. 7, centre of same section enlarged, showing 

 young whorls. Fig. 8, specimen like Fig. 12, in having no keel on the outer whorl. Fig. 9, 

 variety in which both tubercles and keel appear at an earlier stage. Loc. Whitby. Fig. 10, 11, 

 same variety, showing stouter form of young and earlier developed keel. Fig. 12, 13, D'Or- 

 bigny's type, showing the prolonged duration of the smooth stage, and absence of the keel. 

 Fig. 14, adult of var. Gaudryi. Loc. Semur. 



Cal. raricostatum. 3 Fig. 15, Johnstoni-like variety, loc. Balingen. 



i See also Plate VII. Fig. 1, for side view. 2 See Plate VIII. Fig. 1-3. 



8 See Plate I. Fig. 24, 25. 



