Class VI. NAUTILUS. SAIL-SHELL. Q45 



Sect. III. UNIVALVE SHELLS, 



* With a regular spire. 

 GENUS XIX. NAUTILUS. SAIL-SHELL, 



Shell univalve, consisting of compartments or 

 cells, communicating with each other by 

 means of perforations in the septa or par- 

 titions. 



* Spiral ; spires or volutions connected. 



Lin. Tr. viii. 114. Mont. Test. Br. lgi. t. 6. 1. lacus- 



/. 3. id. Sup. 88. TRIS * 



* N. with a spiral shell, compressed, umbili- 

 cated, ridged; of three spires, above convex 

 and connected, apertures half oval; partitions 

 three rayed, perforated ; diameter one fourth 

 of an inch. Fresh water. 



On flags and car ices in Kent and Bucking- 

 hamshire, 



