346 J. E. Duekden — Jamaican Actiniaria : Part I. — Zoanthece. 



Isaurus Duchassaingi (Andres). 



(PI. XVII. A, fig. 4.) 



Zoanthus tuberculatus , . . . Duchassaing, 1850, p. 11. 



Zoanthus tuberculatus, . . . Duchassaing and Michelotti, 1860, p. 327, 



pi. viii., fig. 5. 

 Antinedia tuberculata, . . . Duchassaing and Michelotti, 1866, p. 136, 



pi. vi., figs. 2, 3. 

 Antinedia Duchassaingi, . . . Andres, 1883, p. 330. 

 Isaurus Duchassaingi, . . . M c Murrich, 1896, p. 190, pi. 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 cm. 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. 



