J. E. Duerpen—Jamaican Actiniaria: Part I.—Zoanthee. 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 Brachyeneminz and Macrocnemine. 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. xrx., figs. 2 and 3). 
Similar combinations exist in Palythoa caribea, Duch. and Mich.; but one polyp 
exhibited the full macrocnemic arrangement on both sides, in place of the normal 
brachyenemic (Pl. x1x., 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 :— 
ZOANTHEZA, 
BRACHYCNEMINZ. 
Zoanthus Solanderi, Lesueur. 
Zoanthus flos-marinus, Duchassaing and Michelotti. 
Zoanthus pulchellus (Duchassaing and Michelotti). 
Isaurus Duchassaingi (Andres). 
Gemmaria variabilis, n. sp. 
Gemmaria fusca, n. sp. 
Palythoa mammillosa (Ellis and Solander). 
Palythoa caribea, Duchassaing and Michelotti. 
: 3E2 
