23 



(20.) To his second great division^ Lamarck restricts 

 the title oi Mollusca : these he again subdivides into the 

 five following orders : — 1 . The Pteropoda, which forms 

 a part of our Cephalopoda. 2. The Hydrohranchia^ 

 which includes the JVudibranchia, Scutihranchia, and 

 Tectibranchia of Cuvier ; together with the genera On- 

 chidium, ParmaceUa, Limax, Testacellus, and Vitrina : 

 these genera he places in his section Pneumobranchia, 

 and makes them the passage to his tlm^d order, or the 

 Trachelipodes, in which all the univalve shells are placed. 

 The foiu'th order is composed of the Cephalopoda, or 

 cuttlefish ; and the fifth contains the Heteropoda. 

 The genera belonging to each of these orders are as 

 follows : — 



Order I. PTEROPODA. 



Hyalaea. 

 Ciio. 



Cleodora. 

 Limacina. 



4 



Cymbulia. 

 Pneuraodermon. 



