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



" in either a linear or incrusting manner." Verrill (1869) distinguished the 

 genus Mammillifera from Zoanthus "in having smaller, shorter, or more sessile 

 polyps, and in the tendency to form continuous basal membranes, instead of 

 linear stolons." Hertwig (1882) states that " Zoanthus and Epizoanthus are 

 distinguished from Mammilifera and Palythoa by the fact that, in the former 

 two, the polyps project plainly above the common basis, whilst in the latter two 

 they are united up to the free end by basal ccenenchyma." Andres (1883) 

 distributes the various species partly under Polythoa and partly under Zoanthus. 

 Hertwig (1888), as a result of the researches of Erdmann (1885), separates 

 Mammillifera from Zoanthus by the possession of only a simple mesodermal 

 sphincter muscle. M c Murrich (1889) follows Erdmann in this. Haddon and 

 Shackleton, however, in their " Revision of the British Actinia?" (1891), in a foot- 

 note to Mammillifera, state : — " The position of this genus cannot be settled until 

 the type species have been recovered and sectionized " — the types being Lesueur's 

 Mammillifera auricula and M. nymphcea. A form, covering considerable areas, 

 occurs at Port Henderson and at Drunkenman Cay,* near Kingston, which I 

 have no hesitation in identifying as closely allied to the M. nymphwa, of Lesueur, 

 and with the better description of the species given by Duckassaing and 

 Michelotti for colonies found by them at different islands of the West Indies. 

 An anatomical study of this shows that, not only in the fundamental characters 

 of the brachycnemic arrangement of the mesenteries and the double mesoglceal 

 sphincter muscle, but also in many minuter details of structure, the species agrees 

 with other members of the genus Zoanthus as described by Erdmann, M c Murrich, 

 and Haddon. Lesueur's description and figure of M. auricula, the other type 

 species, leave no doubt that, when found and examined, it will also have the 

 characters of a Zoanthus. 



Since this was first written, Prof. M°Murrich (1896) has obtained from the 

 Bahamas an incrusting form which he identifies as Mammillifera nymphcea, and has 

 shown that it is an undoubted Zoanthus. It is distinct from the Jamaican species 

 (p. 345). 



Following Haddon, M° Murrich removes the species placed in his earlier paper 

 under Mammillifera to Isaurus. 



The use of the sphincter muscle, for specific purposes, is well exemplified in 

 the genus Zoanthus. Differences are readily seen in the figures of the three 

 following species, and these again can be distinguished from the sphincters of 

 others represented elsewhere. A marked difference, in the muscle, exists in 



* The Port Eoyal Cays, known as Gun, Eackum, Drunkenman, Lime, Maiden, South, and South-east 

 Cays, are a group of small coral islands outside Kingston Harbour. They are raised but a little above 

 sea-level, some with and others without vegetation. The shores and shallow-waters around are the usual 

 and most favourable spots for marine collectors. 



