42 McMURRICH. [Vou. III. 
ently in a simple cycle, while upon the surface of the disc, and 
separated from the marginal tentacles by a naked space, are 
numerous tuberculiform or lobed tentacles, arranged more or 
less radially. No sphincter muscle, the musculature through- 
out being very weak. 
I have thought it proper to extend this family somewhat, so 
as to include it in a genus referred by Andres to the family 
Crambactide. My reasons for so doing will be given when 
discussing the genus. 
Genus RuopactTis, Milne-Edwards. 
Synon. -— Metridium (pars) — Ehrenberg, 1834. 
Actineria (pars) — Deshayes, 1837. 
Rhodactis — Milne-Edwards, 1857. 
Rhodactidz with smooth column. Marginal tentacles very 
short and conical ; disc tentacles more or less lobed, arranged in 
two groups, one, consisting of the greater number of tentacles, 
towards the periphery of the disc, and the other separated from 
the peripheral group by a naked space, and consisting of a few 
tentacles only, situated around the mouth, and therefore labial. 
8. Rhodactis Sancti Thome (Duch. and Mich.). (PI. I., Fig. 9; 
Pl LV.) Pigs..2, 3.) 
Synon. — Actinotryx Sancti-Thome — Duchassaing and Michelotti, 1860. 
Actinothrix Sancti-Thome— Andres, 1883. 
This form, first described by Duchassaing and Michelotti (60), 
is made by them the type of a new genus. They, however, rec- 
ognized its similarity to Rhodactzs, the distinction being that 
“les appendices, qui avoisinent la bouche, sont simples et bilobés, 
tandis que la disposition des tentacules placés entre les cou- 
ronnes interne et externe est aussi différents.”” Andres, however, 
considers this statement “quasi inintelligibile,” and believes that 
the species has nothing to do with Rhodactzs, and places it, along 
with the genus Cvambactis, in another family. After having 
studied this so-called Actinothrix, I have come to the conclusion 
that it zs a Rhodactis, the difference between it and Rhodactzs 
rhodostoma being of specific and not of generic importance. 
Rhodactis Sancti Thome@ is not uncommon at New Providence, 
occurring firmly attached to the coral rock in shallow water. It 
