LINN/EAN ARnANGEMENT. ^i'S 



Cyprrra. Shell with the aperture efluse linear ; teetli on both 



sides. 

 Bulla. Shell with the aperture somewhat contracted, oblique. 

 Volala. Shell with the aperture effuse, with the pillar folded. 

 Biiccinuni. Shell with the aperture with a channel to the rig-ht. 

 Slrombus. Shell with the aperture having; a channel to the left; 

 Murex. Shell with the aperture having a straight channel. 

 Trochus. Shell with the aperture compressed, somewhat square. 

 Turbo, Shell with the apertiu'e compressed, round. 

 Helix. Shell with the aperture compressed, moon-shaped. 

 Nerita. Shell with the aperture compressed, half round. 

 Haliotis. Shell with the aperture wide, bored. 



UNIVALVES without a regular spire. 



Patella. Shell an open cone, resting. 



Dentalium. Shell free, awl-shaped, open at each end. 



Serpula. Shell fixed, tubular. 



Teredo. Shell intruded in wood. 



