346 J. E. Durrpen—Jamaican Actiniaria: Part I_—Zoanthee. 
Isaurus Duchassaingi (ANDRES). 
(Pl. XVII. a, fig. 4.) 
Zoanthus tuberculatus,  . ; . Duchassaing, 1850, p. 11. 
Zoanthus tuberculatus,  . ; . Duchassaing and Michelotti, 1860, p. 327, 
pl. viii, fig. 5. 
Antinedia tuberculata,  . ; . Duchassaing and Michelotti, 1866, p. 136, 
pl. vi., figs. 2, 3. 
Antinedia Duchassaingi, . ; . Andres, 1883, p. 330. 
Isaurus Duchassaingi,  . : . M°Murrich, 1896, p. 190, pl. xvii, figs. 6-8. 
Form.—Base firmly adherent, expanding somewhat over the incrusted surface ; 
usually much larger than the diameter of the column; irregular in outline. The 
flattened expansion may be regarded as a slightly developed ccenenchyme ; but, 
although closely associated, the polyps were rarely connected with one another, 
Column variable in shape, may be cylindrical or clavate, generally more 
expanded towards the base ; slightly overhanging so as to present a concave and 
a convex aspect; the capitulum appears as a disc in retracted specimens, and 
is placed obliquely so that the small central aperture indicating the mouth is 
below the upper termination of the column. Proximal part, for from one-third 
to one-half of the total length of the column, smooth, with thin partial annuli 
showing through, which may become depressions on shrinkage; in the later 
state, numerous well-marked longitudinal ridges and furrows may also be 
rendered obvious. The column on its sides and convex aspect bears irregular 
rows of rather large, rounded tubercles, distinct from one another; the concave, 
shorter portion is smooth, giving rise to a marked asymmetry; four principal 
rows, of from five to eight tubercles, alternate with other rows of two or three 
smaller protuberances. Around the margin of the terminal disc is an incomplete 
circle of eight or nine tubercles, separated by deep depressions. These correspond 
with the rows and extend nearly round the margin, diminishing in size towards 
each extremity of the partial circle. 
The flattened or slightly elevated and dome-shaped capitular disc is partially 
enclosed by these, and bears radiating ridges and furrows, not all equally 
developed; eight or nine which alternate with the marginal protuberances are 
more prominent than the one or two groups alternating with them. A depression 
indicates the position of the mouth. One young specimen, 2°5 em. long, is quite 
smooth, having no elevations. In the living condition, the column-wall is firm, 
very tough, and partially transparent, so that the presence of the internal organs 
can be distinguished. 
