PLATE III 



ONTOGENl' OF SIX SPECIES OF CEEITHItTM 



Numbers at the left of the plate indicate the numbers of the volutions. 

 Dotted lines indicate gradual transition from one volution to the next figured. 

 The amount of enlargement is given on the plate; actual measurement of the 

 portion of the shell figured is given below. All the figures on Plates III to IX 

 are from original drawings by the author. 



Fig. 1. Cerithium tuberosioii, fourth volution. 1.6 X .3 mm. 



Fig. 2. Cerithium adansoni, protoconch. .6 X .4 mm. 



Fig. 3. Cerithium adansoni, second volution. .8 X .3 mm. 



Fig. 4. Cerithium adansoni, third volution. 1.1 X .5 mm. 



Fig. 5. Cerithium? nodulosum, fourth volution. 1.9 X 1 mm. 



Fig. 6. Pseudovertagus aluco, fourth volution. 2.2 X 1.1 mm. 



Fig. T. Cerithium lamellosum, protoconch and first volution. .5 X .7 mm. 



Fig. 8. Cerithium lamellosum, third volution. .7 X. 32 mm. 



Fig. 9. Cerithium retardatum, second volution. .5 X. 25 mm. 



Fig. 10. Cerithium retardatum, third volution. .75 X .37 mm. 



