PLATE III. 



Arn. Hartmanni. 1 Fig. 1, la, cast. Fig. 1 shows the thick shell lying on the keel of 

 the cast. Loc. Lyme Regis. 



Cor. kridion. Fig. 2, young. Fig. 2 a, outline of young suture of Fig. 2, enlarged. Fig. 3, 

 cast. The last volution in this represents the living chamber. Loc. Balingen. 



Cor. rotiforme, var. A. Fig. 4-4 a, young smooth stage and suture. Fig. 5, 6, 8, 8a- 10, 

 10 a, older stages of same. Fig. 7, 11-13, pathological cases with pilae crossing the abdomen. 

 Loc. Semur. Fig. 14, 15, 15 a, 16, kridion-like variety of this species. (Fig. 14, loc. Stuttgardt ; 

 Fig. 15, 16, loc. Balingen.) Fig. 17, 17 a, variety with discoidal form and large tubercles, figure 

 reduced to about two thirds, loc. Semur. Fig. 17 b, sutures. 



Cor. Bucklandi, var. sinemuriense. Fig. 18, figure reduced to less than one half, show- 

 ing the divided pilae of the young (sinemuriense stage), and the solid Bucklandian pilae of the 

 adult, loc. Seinur. 



Cor. latum. Fig. 19, young with narrow abdomen. Fig. 22, older stages of same variety, 

 showing affinities for Cor. rotiforme and Bucklandi. Fig. 20, section of young of variety with 

 broader abdomen. Fig. 21, 23, 23 a, older stages and suture of same. Loc. Semur. 2 



1 See Plate II. Fig. 17. 



2 These specimens all appear to be in the nealogic stages of development. 



