PLATE CLIII. 



genus Melitaea, where it now occurs under the name of Melitaea 

 Ochracea. This separation of our preselit species from the Isis 

 genus, we must allow, does not appear to be altogether unjusti- 

 fiable ; we regret only the paucity of actual observation on those 

 curious tribes of beings denominated Zoophytes, when in a living 

 state, to afford us accurate information as to their natural history in 

 general, and the habits of the species of Isis in particular ; for, if 

 upon the ground assumed by these writers, those two genera should 

 stand confirmed by future naturalists, it is more than probable we 

 must advance yet further, and constitute more than two new genera 

 of the Isis genus, as proposed by Linnaeus. One particular dis- 

 tinction of the Melitaea and the Isis, according to those naturalists, 

 is obviously striking : in the Isis, the intermediate or connecting 

 junctures, by which the true or lapideous joints are united together, 

 is of a horny or somewhat cartilaginous nature, and constitute 

 articulations of a more slender form than the true joint or bone ; in 

 Melitaea, those connecting articulations or junctures, on the contrary, 

 are larger than the true joint, and are of a stony nature, more or less 

 porous and striated. This distinction is worthy of notice ; the com- 

 parative magnitude of those joints is less materially deserving of 

 attention, as a generical distinction, than the substance of which they 

 are composed. We are not to forget, however, that there are examples 

 among the marine tribes of beings, in which the cartilaginous sub- 

 stances of the living body become in some degree ossified after death ; 

 examples in which the ligatures of certain shells, which are decidedly 

 cartilaginous, become afterwards of a stony nature ; and there are 

 besides those, some other appearances in nature that might be noticed 

 as somewhat analogous, although they may not precisely bear upon 

 the point before us. 



