166 J. E. DurrpEn—Jamaican Actiniaria : 
The parietal mesenterial stomata are small, circular apertures, located a little 
distance from the column-wall just below the sphincter muscle; the perioral are 
somewhat larger. 
Gonads were restricted in one specimen to the second cycle of mesenteries. 
Prof. M*Murrich (1889, p. 40) found that “‘ the reproductive organs were present 
on all the mesenteries, with the exception probably of the directives.”’ 
This species is very abundant in the neighbourhood of the coral reefs around 
Jamaica, wherever these have been examined, sometimes partly buried in the sand, 
but more often attached to rocks. Isolated individuals may occur, but usually a 
number are closely aggregated, so close, at times, as to give rise to a polygonal 
outline of the dises, the result of mutual pressure. The associate habit and often 
the presence of more than two gonidial grooves are no doubt indicative of reprodue- 
tion by fission; and Prof. M‘Murrich obtained several specimens at the Bahamas 
in various stages of division. A small, brightly-coloured Crustacean has been 
found on one or two occasions living on the disc; but this commensalism is 
evidently not so constant a feature of the West Indian species as of those described 
and figured by Mr. Saville-Kent, from the Australian Barrier Reef. Here a 
brilhantly-coloured fish and one or two species of prawns are commensal with the 
polyps, and may pass in and out of the gastric cavity. 
My reasons for regarding the Discosoma anemone, described by M*Murrich, 
as the Actinia helianthus, of Ellis, are given at the end of the description of the 
next species. 
Genus. _HOMOSTICHANTHUS, n. g. 
Discosomidz, in which the tentacles are slightly knobbed and arranged in 
numerous peripheral cycles and radiating rows, a single row communicates 
with each endoccele and exoceele. Column-wall devoid of verrucee ; dise much 
folded. ‘Two deep gonidial grooves. Sphincter muscle restricted.* 
The generic term has reference to the practical similarity of all the rows of 
tentacles, both endoceelic and exoccelic. 
* Prof. Haddon (1898, p. 432) employs this useful term for an endodermal sphincter muscle, in form 
intermediate between the diffuse and the truly circumscribed types. It refers to an intermediate stage, 
in which the mesogleeal plaitings, for the support of the musculature, do not arise from a common axis, but 
from several principal axes of less complexity. He further suggests ‘‘constricted”’ for the typical cir- 
cumscribed muscle. (cf. figs. 8 and 7, Pl. xmr., ‘‘ diffuse endodermal muscle’’; fig. 6, Pl. xm., ‘‘ restricted 
endodermal muscle”’; figs. 1, Pl.’ x1v., fig. 2, Pl. xv., “circumscribed (constricted) endodermal muscle ”’; 
also, ‘‘ageregated,’? M°Murrich, 18938, p. 152, pl. xxii, fig. 23.) 
