J. E. Durrnpen—Jamaican Actiniaria: Part I.—Zoanthee. 345 
Gonads (Pl. xvut. A, fig. 4).—Ova and spermaria are borne in close proximity 
on the perfect mesenteries, both above and below the cesophagus. They were 
met with in three specimens taken from the same colony, but none were present in 
several examples sectionized from another colony. 
Coenenchyme.—The ccenenchyme is of similar structure to the body-wall, but 
the mesogloea is much thicker and broken up by large ciliated ccelenteric canals 
passing in all directions; the endodermal lining is loaded with zooxanthellae, and 
has a weak musculature. Isolated cells with fine processes, and the smaller 
ectodermal canals occur. 
For some time during the preparation of this Paper, I had regarded this 
species, with little or no hesitation, as the Mammillifera nymphea of Lesueur 
(1817). In the meantime, Prof. M*Murrich identified, with some amount 
of uncertainty, a form from the Bahamas as Lesueur’s species. The external 
characters of the Jamaican representative agree with those of the Bahaman, as 
far as the Jatter are given, but a comparison of the sphincter muscles shows that 
they are undoubtedly distinct. Prof. M*Murrich, from an examination of my 
material and slides, entirely agrees with this. Whether his identification of the 
Bahaman form with that which Lesueur described be correct or not, it seems 
best that his conclusion should be followed for the future, seeing that with the 
addition of the anatomical features, the characters of the species are definitely 
fixed once for all. There must nearly always be an amount of uncertainty in 
identifying the species of the older authors, where external characters only were 
taken into account. I have therefore changed my manuscript identification of 
this species to that of Mammillifera pulchella of Duchassaing and Michelotti (1866), 
a form these authors regarded as a doubtful variety of M. nymphea. 
Isaurus, Gray, 1828. 
Large brachyenemic Zoanthez, with a single mesoglceal sphincter muscle. 
The body-wall is unincrusted; the ectoderm discontinuous; ectodermal and 
endodermal bays and small canals in the mesogloea. Moncecious or dicecious. 
Polyps in small clusters or solitary. 
Prof. Haddon and Miss Shackleton give (1891, pp. 682-4) a full discussion of 
the genus defined by them as above. They dwell particularly upon the reason 
-why it should not be merged into the genus Mammillifera of Lesueur, as, 
accepting the characters Erdmann gives (1888, p. 35), has been done by 
M*Murrich (1889, p. 117). In his more recent paper (1896, p. 191), the latter 
author adopts Jsaurus. 
TRANS. ROY. DUBL. SOC., N.S. VOL. VI., PART XIV, 3G 
