J. E. Dueeden — Jamaican Actiniaria : Part I. — Zoanthece. 361 



radiately. New individuals arise mostly along the side of those forming the 

 periphery of a colony. 



Colour. — Coenenchyme and column pale yellow or cream colour, sometimes 

 brown ; tentacles and furrowed portion of disc pellucid ; middle of disc grey, due 

 to presence of sand-grains ; lips white. 



Dimensions. — Average height of polyps 1*3 cm., maybe only - 6 cm. or 1/8 cm. ; 

 diameter of flat expanded disc 1*2 cm. ; average diameter of columns 0"6 cm. ; 

 distance of centres of continguous polyps in retraction about 07 cm. ; inner 

 tentacles - 2 cm. long. Colonies of various sizes are met with, but usualty from 

 3 to 8 cm. across. 



Locality. — Jamaica: found in abundance firmly encrusting the coral-rock in 

 shallow water, mostly in the region of the breakers, at the Cays outside Kingston 

 Harbour, and at other points around the coast. 



Range. — Guadaloupe and St. Thomas (Duchassaing and Michelotti). 



Column-wall (PI. xix., fig. 1). — The column- wall of the individual polyps is 

 separable from the coenenchyme for only a short distance at the upper surface of 

 the colony. The two are not very thick compared with the size of the polyps. 

 In transverse sections the coenenchyme may be from Ol to 02 cm. in thickness, 

 while the polyps are from - 6 cm. to - 3 cm. in diameter. 



The ectoderm is a thick layer, and continuous over the outer surface of a 

 colony ; a cuticle, devoid of foreign adhering matter, is present. Its internal 

 limitations are occasionally irregular, due to the incrusting sand-grains ; these 

 latter are limited to the inner part of the ectoderm and to the niesoglcea. The 

 outer portion of the ectodermal cells is largely glandular ; the middle and inner 

 parts contain the nuclei, numerous zooxanthellse, and occasional large oval 

 colourless nematocysts showing the internal thread. 



The mesoglcea varies in thickness, appearing in sections as a matrix in which 

 the cylindrical polyps are embedded. The incrusting material is practically dis- 

 tributed throughout ; in the periphery of a colony however it is rather limited to 

 the outer half. The foreign objects are mostly calcareous, but a few siliceous 

 sponge spicules and an occasional Foraminiferal and Eadiolarian test may be 

 present. Abundant small and large cell-islets or short canals are distributed 

 with considerable uniformity ; the latter in some sections exhibit somewhat of a 

 concentric arrangement around the individual polyps, and may be seen communi- 

 cating with the canals in the mesenteries. In others, a canal appears opposite 

 nearly all the mesenteries. The islets contain zooxanthellse and large oval nema- 

 tocysts ; the smaller islets have the protoplasm exhibiting peripherally a fine 

 morula-like appearance, with a central more deeply staining nucleus. A similar 



TBANS. EOT. DOT. SOC, N.S. VOL. TI., PAEI XIT. 3 I 



