J. E. Duerden— Jamaican Actiniaria : Part I. — Zoanthece. 363 



mesenteries on each side, but in one polyp there are ten on one side and nine on 

 the other ; in another seven and nine, arranged as shown in fig. 3. The funda- 

 mental distinction of the Zoanthidse into Brachycneminae and Macrocneminse is 

 departed from in the sections of two polyps represented. In fig. 2 it is seen that 

 the normal brachycnemic arrangement holds on the left side, while the macrocnemic 

 is present on the right side. This is also the case in fig. 3, only the order is 

 reversed. 



The manner of the connexion of the mesenteries to the oesophagus is best 

 shown in fig. 2. Beyond the sulcar directives there is a considerable interspace 

 before the other mesenteries are reached, and then the interspaces are about equal. 

 The mesenteries are very thin near their attachment to the column-wall, but 

 enlarge a little to form the basal canal. The imperfect mesenteries do not 

 project far. The endoderm contains zooxanthellae and pigment matter, and the 

 mesoglcea is extremely thin. The parieto-basilar muscles are well developed. The 

 basal canal is usually rounded, and contains numerous large oval nematocysts. 

 The reflected ectoderm and mesenterial filaments present the usual structure. 

 The digestive endoderm is very thick and granular. 



Gonads. — No gonads were present in numerous examples sectionized. 



Ccenenchyme. — The basal portion of the ccenenchyme is very crowded with 

 canals in communication with the basal canals in the mesenteries and containing 

 pigment granules and large oval nematocysts. Ccelenteric canals connect one 

 polyp with another. 



This species, first described by Ellis and Solander, is one of the two original 

 representatives of the genus Polythoa of Lamouroux. The material upon which it 

 was founded was originally obtained by Sir Hans Sloane from Jamaican waters, 

 probably about the year 1687, when Sloane visited the island. The specimens 

 were deposited by him in the British Museum ; the collections of the famous 

 naturalist and physician forming the nuclei of that national institution. Sloane, 

 however, in his " Voj'age," which deals largely with the Natural History of 

 Jamaica, has no description of the objects beyond that given on the plate con- 

 taining his three figures, u Lapidis astroitidis sive stellar is primordial implying that 

 this, along with the Alcyonium ocellatum, of Ellis and Solander, are the beginnings 

 of the stony star-like corals, so abundant in the seas around. 



Ellis and Solander first named, described, and again figured Sloane's specimen. 

 Although their description, " This whitish leather-like Alcyonium is spread over 

 rocks, with many convex teat-like figures, hollow in the middle, with a faint star- 

 like appearance, and united close together," is rather incomplete for purposes of 

 identification, still the excellent figure they give of a colony leaves me little 

 hesitation in considering the form described above as the same these two authors 



312 



