CHITON. PATELLA. 63 



" PhylUdUma includes the genera — 



Phyllidia. 

 Chitonella. 



Chiton Coat of mail. 



Patella Patella, or limpet. 



'' The Chiton moves like the Patella, upon a 

 disk, or foot. 



" The body of Patella is entirely covered by 

 the shell. You may have many opportunities of 

 examining the British species. P. pelluclda is 

 very transparent, with blue lines. 



'•' The family Semi-phyllidiana contains 



Pleurohranchus. 



Umbella Patella. 



*' The Umbella shell is flat and white, and is 

 sometimes four inches in diameter. It is common 

 in the Isle of France: there is another from the 

 Mediterranean. 



'' Calyptracea is a larger family : it has many 

 genera taken from Patella : 



Parmorphorus, Thracian-shield. 



Emarginula, 



Fis'iurella, 



ni . r Patella. 



PUeopsis, 



Calyptroia, 



