360 ^J. E. Dueeden — Jamaican Actiniaria : Part I. — Zoanthece. 



Form. — Polyps smooth, rigid, cylindrical, arranged in a somewhat rectangular 

 manner ; the smooth ectoderm is easily rubbed off exposing the mesoglcea below, 

 with a roughened surface due to the foreign incrustations ; in retraction rounded 

 or somewhat flattened above, free for a short distance beyond the surface of the 

 ccenenchyme. In the living state, or when preserved in formalin without con- 

 traction, the polyps are equally free all round, and so closely arranged that they 

 are separated above only by polygonal dividing lines, none of the coenen chyme 

 being visible (fig. 7). Specimens which have been preserved in alcohol and in 

 which shrinkage has taken place are not equally free on all sides, but con- 

 nected with one another by four (may be three or five when the polyps are 

 not arranged in a rectangular manner) higher, occasionally grooved, ridges of 

 ccenenchyme, and rounded depressions of ccenenchyme, are seen in the spaces 

 between (fig. 8). A central, slightly depressed aperture remains in retracted 

 polyps, and occasionally three to six longitudinal wrinklings along the free portion 

 of the wall of the peripheral potyps are present in specimens preserved in alcohol, 

 and also transverse wrinklings. The amount of the free portion varies according 

 to the state of extension or retraction of the polyps in a colony. Usually in 

 complete retraction about 04 cm. are free ; in partial retraction, when the full 

 capitular ridges can be counted, and in full expansion, about 0*6 cm. are free. 

 In almost complete retraction the capitular ridges are wedge-shaped with very 

 narrow furrows ; as the polyps slowly open, the ridges become more convoluted or 

 laterally undulating, and finally appear as so many acute marginal denticulations. 

 These, as already shown above, are usually from 18 to 20 in number. The 

 polyps of three other colonies from South Cay had a very regular number of 

 ridges as follows : — 



A.— 19, 18, 18, 18, 18, 18, 18, 19, 18. 



B.— 19, 18, 18, 18, 18, 18, 18, 18, 19, 18, 19, 18, 19. 



C— 18, 21, 18, 19, 18, 18, 18. 



Tentacles very short, smooth, acuminate, dicyclic, inner row opposite the mar- 

 ginal denticulations, slightly entacmseous, overhanging in extension, 18 to 20 in 

 each row. Disc cup-shaped in partial, and saucer-shaped in full, extension, but 

 with the central part appearing as a dome and bearing the slit-like mouth at the 

 apex. The peripheral zone of the disc is thin-walled, pellucid, smooth, devoid of 

 incrustations, and raised into elevations and grooves corresponding with the 

 number of tentacles, of which it appears as a continuation. In full extension it 

 is flat or may be arched over ; in partial extension it is nearly vertical. The 

 central part of the disc is smooth, but contains a few incrustations. The species 

 usually occurs in small, rather high colonies, closely associated with one another, 

 but separated by deep channels. The incrusting base is much smaller in area 

 than the distal surface, the peripheral polyps being arranged obliquely or 



