PLATE III 



ONTOGENY OF SIX SPECIES OF CEBITHIUM 



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. Ceiithium tuberosum, fourth volution. 1.6X.3mm. 



Fig. 2. Ceriihium adansoni, protoconeh. .G X .4 mm. 



Fig. 3. Cerithiunt ciditnsouU second volution. .8 X .3 mm. 



Fig. 4. Cerithiuvi adanmni, third volution. 1.1 X .5 mm. 



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



Fig. 6. Pseudovcrtagiis aliieo, fourth volution. 2.2 X 1.1 mm. 



Fig. 7. Cerithium himeUosuvi, protoconeh and first volution. .5 X .7 mm. 



Fig. 8. Cerithium lamcUosuiu, 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. 



