J. E. Duekden — Jamaican Actiniaria: Part I. — Zoanthew. 341 



marked zones, all of nearly equal breadth ; an outer non-staining ciliated portion ; 

 a middle deeply-staining zone with oval-shaped nuclei, granular gland cells and 

 narrow nematocysts ; and an inner, slightly narrower, nervous layer, con- 

 taining a few circular nuclei, and a little pigment matter. The mesogloea and 

 endoderm are each narrow. In transverse section, the oesophageal groove is not 

 very pronounced, and the ectoderm is thrown into folds in some cases, in others not. 



Mesenteries. — The mesenteries are brachycnemic in arrangement and very 

 thin. In one specimen, twenty-four pairs were present ; in another, twenty-one. 

 The endoderm is well developed, made up almost entirely of zooxanthellae and 

 medium-sized, oval-shaped nematocysts. The mesogloea is folded and plaited 

 on one side for the support of the longitudinal retractor muscle. A basal canal 

 is developed in some a little distance from the column-wall, but is not present 

 in others. 



The reflected ectoderm, mesenterial filaments, and endoderm swollen in the 

 lower region, are similar to those figured and described by M c Murrich (1889, 

 p. 115, pi. vii., figs. 3, 4), and the endoderm has embedded in it what I take 

 to be the delicate acicular siliceous spicules referred to by him. The digestive 

 endoderm is not so thickly developed in the previous species. The Driisenwulst 

 of von Heider (1895, p. 129) can be well studied. 



Gonads. — None of the numerous specimens examined were fertile. 



I identify this very common Jamaican form as the Zoanthus flos-marinus of 

 Duchassaing and Michelotti, rather from the description by Prof. M c Murrich of 

 specimens from the Bermudas (1889). The diagnosis of the original authors is 

 very incomplete for this variable genus. They state the tentacles to be thirty-six, 

 while the later writer gives them as fifty to sixty in number, a number agreeing 

 with the Jamaican examples. Andres places it amongst his Zoanthi clubii. 



It may readily be distinguished from Z. Solanderi by its smaller size, usually 

 clavate form, and stolon-like ccsnenchyme ; and from Z. pulehellus by never 

 forming a broad lamellar ccenenchyme. 



Zoanthus pulehellus (Duchassaing and Michelotti). 



(PI. XVII. a, fig. 3.) 



Mamillifera pulchella, Duchassaing and Michelotti, 1866, p. 137, pi. vi., fig. 4. 

 Polythoa (Mammothod) nymphosa, Andres, 1883, p. 320. 



Form. — Polyps erect, cylindrical, short or elongated, smooth, usually closely 

 grouped, rising from a thin, tough, lamellar, incrusting ccenenchyme. In re- 

 traction, either a little enlarged above or of the same diameter throughout, 

 terminating in a rounded or slightly conical manner, and showing a central 



