16 



ORDER OF CLASSES. 



(namely, salpa, ascidia, etc.) and aggregated acephala, 

 (botryllus, pyrosoma, etc.) under the acephala, but with 

 an acknowledgment of the propriety of separating them 

 into a distinct class : to this class has been given the 

 title of tunicata. 



Retaining the cirrhopoda, or barnacles, in the pre- 

 sent sub-kingdom, the arrangement of the classes will 

 stand as follows, reversing the order of Cuvier, and 

 ascending, instead of descending, the scale of organic 

 being. 



SUB-KIXGDOM, MOLLUSC A, OR HETEROGANGLIATA. 

 CLASS. 



1. Cirrhopoda. 



2. Brachiopoda. (Palliobranchiata. Owen.) 



3. TUXICATA. 



4. CoxcHiFERA, or Acephala. 



5. Gasteropoda. 



6. Pteropoda, 



7. Cephalopoda. 



In these we shall find an abundance of interesting 

 and instructive objects. We must glance at the land, 

 but we shall have to do chiefly with the ocean, of which 

 a poet has said : 



Tlie floor is of sand, like the mountain drift, 

 And the pearl-shells spangle the flinty suon- ; 



From coral rocks the sea-plants lift 

 Their boughs, where the tides and billows flow ; 



