344 J. K. DuerpEN—Jamaican Actiniaria: Part I.—Zoanthee. 
the cavities larger and more circular, as in the figures of the two previous 
species. ‘The sphincter in this species differs from that of the two former in that 
the proximal part commences above with numerous small cavities. 
Tentacles—The ectoderm of the tentacles is ciliated and without any cuticle 
or sub-cuticla; it is much thicker than that of the column, and small nematocysts 
occur in restricted areas. The weak ectodermal muscle is supported on minute 
plaitings of the mesoglea. The mesoglea is thin, with a few isolated cells. 
The endoderm is thicker than the ectoderm, leaving scarcely any lumen in 
retraction. Abundant zooxanthelle, small oval nematocysts, and a weak 
endodermal muscle are met with. 
Dise.—-The ectoderm of the dise is nearly as thick as that of the tentacles ; 
the nuclei stain very deeply ; an ectodermal musculature occurs. The mesogloea 
is broad, destitute of cell-enclosures, and contains a few isolated cells. The 
endoderm is like that of the mesenteries, and has an endodermal musculature. 
Esophagus.—The ectoderm in the cesophagus is rather broad and ciliated, and 
thrown into about eight deep longitudinal folds on each side, partially followed 
by the mesoglea; the cesophageal groove is elongated, occupying in some 
sections about one-third the transverse area of the cesophagus. The appearance 
is much the same as that figured by M*Murrich for the stomadceum of Z. sociatus. 
The ectoderm contains an occasional small oval nematocyst, in addition to the 
usual abundant narrow ones, and also a little pigment matter on its inner border. 
The mesogloea is thinner than the ectoderm, and contains no cell enclosures. 
Mesenteries (Pl. xvi. a, fig. 4).—The number of mesenteries varies, twenty- 
eight perfect ones occurring in one specimen, and twenty-six in another, corre- 
sponding with the varying number of tentacles. A slight parieto-basilar muscle 
is found on each side. The endoderm has zooxanthellee and small nematocysts. 
A few isolated cells occur in the mesoglea. Below the cesophagus, the mesen- 
teries, with the mesenterial filaments, assume, in transverse section, first a sagittate 
appearance, and lower a clavate form; in the lower region of the cesophagus, 
the reflected ectoderm has the characteristic pinnate appearance, the whole 
corresponding with that described and figured by Haddon and Shackleton for 
Z. Macgillivrayi (1891, p. 681). Nematocysts occur. 
A very weak musculature extends along the whole surface of both sides of the 
mesentery, the mesoglea being slightly plaited in places. A single basal canal 
passes the whole vertical length; in the perfect mesenteries, it is oval in section 
in the distal region, but becomes elongated and stretches nearly the whole width 
in the basal part of the polyp. 
In the imperfect mesenteries, the basal canal remains approximately circular 
in section. ‘The tissue inside the canals is of the same character as the endoderm, 
being crowded with zooxanthelle and nematocysts. 
