Mp... 2..] ACTINIARIA OF THE BAHAMAS. 71 
The occurrence of Lebrunea neglecta in shallow water in the 
West Indies is of considerable interest in view of the fact that 
the other members of the sub-tribe Dendromeline, so far as is 
known, occur in deep water — 2160 and 1375 fathoms — off the 
coast of Chili. I think there can be little doubt but that Hert- 
wig’s Ophiodiscz are related to Lebrunea in the possession of the 
peculiar pseudotentacles ; and this being the case, we have two 
related genera, the only ones known of the family, living under 
conditions apparently totally different. Ophzodiscus lives in a 
region in which prevail absolute darkness, almost total stillness, 
and a comparatively very low temperature, whereas Lebrunea 
is exposed to the full light of the sun, to water constantly in 
motion, and to a perennially high temperature. This seems at 
first sight to be a decided anomaly, but I think an explanation 
is to be found in a suggestion made by Semper.! He has shown 
that a great number of genera of Holothuridz, which were gen- 
erally supposed to be boreal, living at considerable depths in 
northern seas, occurred in the Philippines, and only at a mod- 
erate depth. The conclusion follows that it is not so much the 
absolute temperature which limits the distribution of animals as 
the exposure to great or more or less sudden variations, Al- 
though the absolute temperatures to which Ledrunea and Ophio- 
discus are exposed differ enormously, yet in both cases it is an 
equable temperature, an almost constant great degree of cold in 
the case of the latter, while Ledrunea lives in the warm waters 
of one of the most equable climates known. 
To return to the question of distribution, I think that the rela- 
tionships of the West Indian Actiniaria to those of the Pacific is 
another piece of evidence in favor of a past communication be- 
tween the Atlantic and Pacific oceans through the Isthmus of 
Panama. It is a case in accordance with what is known regard- 
ing the similarities in the fishes, mollusca, and Holothurians of 
the two sides of the Isthmus. 
November 21, 1888. 
1C, Semper, Reisen im Archipel Philippinen. Theil II., Bdi. “ Holothurien.” 
Wiesbaden, 1868. 
