610 PHILOSOPHY OF ZOOLOGY. 



of many fossil species, and the genera under which they 

 may be distributed, have been successfully elucidated by 

 Mr J. S. MILLER, in his valuable work on the animals of 

 this tribe *. 



Class II. ACALEPHA. 



This class was instituted by CUVIER, for the reception of 

 the animals of the genera Actinia and Medusa of LINN^US. 

 The integuments are soft, and frequently gelatinous. The 

 stomach and intestines never float distinct in a particular ca- 

 vity. The traces of circulating vessels are obscure. CU- 

 VIER divides the genera into two tribes, such as are fixed, 

 and such as are free. 



Order I. 



Base opposite the mouth, adhering to other bodies. In 

 this order there are two kinds of adhesion, temporary and 

 permanent. The first kind is exhibited in the genera Actinia 

 and Lucernaria ; the latter in Zoanthus. The first and last 

 of these genera, however, agree in so many other respects, as 

 to forbid their separation, by the intervention of the second. 

 Indeed, in this case, (or as is still better illustrated in the 

 case of the Oyster and Scallop) the circumstance of being 

 fixed or free, exercises but little influence on the organiza- 

 tion. 



1st Tribe. 



Tentacula uninterruptedly surrounding the oval disc. 

 Of the genus Actinia we have many species in our seas, 

 and the Mammaria mammilla, likewise a native, appears to 

 belong to Zoanthus. 



2d Tribe. 



Tentacula on the margin of the oral disc disposed in 

 tufts. This includes only the genus Lucernaria, five spe- 



f " A Natural History of the Crinoidea," 4to, Bristol, 1821. 



