340 Dana on the Classification of Animals 
Alphatypic, niiiiine - - + 1. Vertebrates. 
Betatypic, - - oo) tat - 2. Articulates. 
Gammatypic, - - - - - 8. Mollusks, 
Degradational, - - - - - 4, Radiates. 
An important dynamical distinction between Mollusks and 
oids, or the deat and Ascidians, which are mostly attached 
é : 
