148 J. E. DurrpEn—-Jamaiean Actiniaria : 
covering nearly the whole of the disc, while there is a marked difference, both in 
form and histology, between the marginal and discal tentacles in Actinotryx. 
In important anatomical details, such as the deep stomodeeal folds, absence of 
gonidial grooves, and ciliated streak, Actinotryx and Ricordea are related; but, 
excepting perhaps the last mentioned, evidently not much reliance can yet be 
placed upon these for indicating broader relationships. 
It is a question of choosing between external characters, and internal anatomy 
and histology as the chief factors of relationship. In the order Stichodactyline, 
at any rate, I am of opinion that the best results will be attained by giving the 
greater prominence to the arrangement of the tentacles among the former. The 
frequent multi-oral condition of the disc occurring in both, must assuredly be 
looked upon as a specific peculiarity. 
Haddon (1898, p. 477) includes the four genera, Rhodactis, Actinotryx, 
Ricordea, and Heteranthus in the family. The second genus was instituted by 
Duchassaing and Michelotti (1860, p. 45) for a West Indian form, which later was 
regarded by M°Murrich as allied to the Rhodactis rhodostoma of the Red Sea, and 
was therefore transferred to that genus. From details of this species supplied 
by Dr. Carlgren, Haddon (p. 477) considers that the two should remain as 
distinct genera, and this is the conclusion I have followed. 
Genus.—ACTINOTRYX, Duchassaing & Michelotti. 
Actinotryz, . . Duchassaing and Michelotti, 1860; Andres (Actinothrix), 
1883 (pars); Haddon, 1898. 
Rhodactis, . . M*Murrich, 1889. 
Rhodactide, in which the column is smooth. Marginal tentacles short, in two 
or three series, but forming only one cycle; inner tentacles dendritic or lobed, 
partly separated into a middle discal group and a perioral group. Sphincter 
muscle feeble or absent. An ectodermal muscular layer on the column-wall and 
stomodeum. Stomodzeum deeply furrowed. No gonidial grooves. Mesenterial 
filaments devoid of ciliated streak. 
The history of the genus has just been given under the discussion on the 
family. 
Actinotryx Sancti-Thome, Duch. & Mich. 
(AG XG 1 SOS Ol sib, wes Gy G3 JEIL seiilip, ste, &)) 
Actinotryx Sancti-Thome, Duchassaing & Michelotti, 1860, p. 45, pl. vit., 
fig. 2; 1866, p. 39. 
Actinothriz Sancti-Thome, Andres, 1883, p. 509. 
Rhodactis Saneti-Thome, M°*Murrich, 1889, p. 42, pl.i., fig. 9, pl. iv., figs. 2, 3. 
