330 J. E. Durrpen—Jamaican Actiniaria: Part I.-—Zoanthee. 
second pair may be composed of two perfect mesenteries (Macrocnemine). In 
the remaining pairs of mesenteries, of both divisions, this order is reversed, so 
that the perfect mesentery is sulear and the imperfect is suleular. The latter 
series of mesenteries are bilateral as regards the polyp, and arise independently 
(z.e. neither in pairs nor symmetrically on each side) in the exoccele on each side 
of the sulcar directives, in such a manner that the sulcular are the oldest and the 
sulcar the youngest. Only the perfect mesenteries are fertile or bear mesenterial 
filaments. A single sulcar cesophageal groove is present. The mesogloea of the 
body-wall is traversed by irregularly branching ectodermal canals or by scattered 
groups of cells. The body-wall is usually incrusted with foreign particles. The 
polyps are generally grouped in colonies connected by a ccenenchyme, the 
celenteron of each polyp communicating with that of the other members of 
the colony by means of basal endodermal canals. 
Family. ZOANTHID, Dana, 1846. 
(With the definition of the Group.) 
Sub-family. Bracuycnemina#, Hadd. and Shackl., 1891. 
Zoanthez in which the sulcar element of the primitive sulco-lateral pair of 
mesenteries is imperfect. 
GENERA. 
Zoanthus, Lamarck, 1801. 
Isaurus, Gray, 1828. 
Gemmaria, Duchassaing and Michelotti, 1860. 
Palythoa, Lamouroux, 1816. 
Sphenopus, Steenstrup, 1856. (Not represented in the West 
Indian collections. ) 
Sub-family. Macrocnemina, Hadd. and Shackl., 1891. 
Zoantheze in which the sulear element of the primitive sulco-lateral pair of 
mesenteries is perfect. 
GENERA. 
Epizoanthus, Gray, 1867. 
Parazoanthus, Haddon and Shackleton, 1891. 
One of the two type species of the genus Mammillifera, established by Lesueur, 
having been shown by M°*Murrich (1896) to possess all the characters of a 
Zoanthus, and there being every probability that the other type species, when 
discovered, will have the same, this genus, formerly included in the Zoanthide, 
can no longer be recognized (see p. 334). 
With the exception of an irregular arrangement of the mesenteries in the 
