364 J. KE. Durrpen—Jamaican Actiniaria: Part I.—Zoanthee. 
had under consideration. The dimensions, amount of the polyps not immersed in 
coenenchyme, and the general form of the colony well agree. I feel all the more 
assurance in this seeing that similar specimens may be collected in abundance 
from what we may regard as the original locality of the type. It is not at all 
improbable that Sloane obtained his examples from precisely the same Cays, these 
being, as already mentioned, the usual and most favourable spots for marine 
collectors. 
Duchassaing and Michelotti (1860) describe as P. ocellata a form which, in their 
later paper (1866), they place under P. mamillosa. They also regard the Corticifera 
Jlava of Lesueur as a variety. It seems pretty evident that these authors, taking 
the number of tentacles as a criterion, introduced some little confusion, so that it 
is now very difficult, if not impossible, to ascertain what forms they are really 
describing. 
There is nothing appearing in the original description and figure of P. cinerea 
which is not met with in the large amount of material of P. mammillosa which has 
come under my observation, the colour, form of the original polyps, and incrus- 
tations of the latter presenting all the variations ascribed to the former, while the 
number of tentacles exactly corresponds. 
The species is readily distinguished a situ from the next one by its habit of 
growth, occurring mostly in numerous, closely associated, irregularly shaped, 
small, high colonies, separated by channels 2 or 3 cm. across. The colonies are 
usually from 8 to 10 cm. in diameter, but may be more. The individual polyps 
are also larger, and appear to open more readily and constantly, and to have a 
greater free distal portion. 
The larger number of capitular ridges, tentacles, and corresponding mesenteries 
is evidently constant. The variations in transverse dimensions are more clearly 
indicated in sections. In the present species the diameter is often 0:6 cm., while 
in the next it is rarely more than 0°35 em. 
Histologically I have not been able to detect much specific difference. 
Numbers of sections have been examined from various colonies, some with the 
incrustations ¢ situ and others decalcified. Although the incrustations are 
abundant and uniformly distributed throughout the colony, the mesoglea is 
apparently not so crowded with them as in P. caribea. 
The basal canals appear more rounded, and perhaps the internal pigmentation 
is not so dense in the present example; also, as shown in the figure, the cavities 
of the sphincter muscle are not in such a regular row. 
