J. E. Dueeden — Jamaican Actiniaria : Part I. — Zoanthece. 331 



genera Gemmaria and Palythoa, referred to below, nothing of importance has 

 occurred differing from the diagnoses, mainly anatomical, of the tribe and genera 

 given in the works of the writers referred to above. 



Since the arrangement of the mesenteries in the Zoanthese, which differs from 

 that met with in all other Actiniaria, was first fully elucidated, it has also been 

 recognized that the group presents a further distinction into two sub-divisions 

 dependent upon the nature of the second pair of mesenteries on each side of 

 the sulcular directives, according as the pair consists of a perfect and imperfect 

 mesentery, or of two perfect mesenteries. The former was first termed by 

 Dr. Erdmann the " microtypus," and the latter the "macrotypus" ; a distinction 

 emphasized later by Haddon and Shackleton (1891) in the formation of the two 

 sub-families Brachycneminse and Macrocneminas. Apparently no variation from 

 these two seemingly well-fixed divisions has since been noted. It is therefore 

 interesting to find that, in West Indian species of the genus Gemmaria and of 

 Palythoa, an irregular condition has been met with. In Gemmaria variabilis, n. sp., 

 a specimen sectionized showed the normal brachycnemic arrangement on one side 

 and the macrocnemic on the other. In a colony of Palythoa mammillosa, Ell. and 

 Sol., one polyp was normally brachycnemic on the right, but macrocnemic on the 

 left side ; and in another polyp, in the same colony, the 'brachycnemic condition 

 was on the left side and the macrocnemic on the right (PI. xix.a, figs. 2 and 3). 

 Similar combinations exist in Palythoa carilcea, Duch. and Mich. ; but one polyp 

 exhibited the full macrocnemic arrangement on both sides, in place of the normal 

 brachycnemic (PI. xix., fig. 7). 



It is thus clear that in these three species, at least, the fundamental distinction 

 of the microtype and macrotype is not sufficiently fixed, so that both may appear 

 in one colony, or even on opposite sides in the same individual. In a number of 

 specimens examined the majority are, however, normal. 



In the present communication the following ten species are described : — 



ZOANTHEiE. 



Beach ycnemin^;. 



Zoanthus Solanderi, Lesueur. 



Zoanthus flos-marinus, Duchassaing and Michelotti. 



Zoanthus pulchellus (Duchassaing and Michelotti). 



Isaurus Duehassaingi (Andres). 



Gemmaria variabilis, n. sp. 



Gemmaria fusca, n. sp. 



Palythoa mammillosa (Ellis and Solander). 



Palythoa caribsea, Duchassaing and Michelotti. 



3E2 



