104 NATURAL SCIENCE [February 



with branching and arborescent tentacles ; these, as already shown, 

 being absent in the former, but prevalent in the latter. 



As yet we know very little of the Actinology of the South 

 Atlantic, that is, along the West Coast of Africa and the East Coast 

 of South America. Collections from these parts and the intervening 

 islands are great desiderata. 



The present state of our knowledge with regard to the geo- 

 graphical distribution of the most important groups of the Actini- 

 aria appears to be best summarised as follows : — 



(1) North Atlantic Region. — Al^undauce of Sagartidae and 

 Bunodidae ; practical absence of Stichodactylinae and Zoantheae, 

 except Macrocneminae. 



(2) Carihbco-Facijic Region. — Numerous Sagartidae and Buno- 

 didae ; ^ most of the Stichodactylinae and all Zoantheae ; absence of 

 Thalassianthidae and Cryptodendridae. 



(3) Imlo-Pacific Region. — Fewer Sagartidae and Bunodidae ; 

 numerous Zoantheae, Stichodactylinae, and especially Thalassianthidae 

 and Cryptodendridae. 



Descending to greater detail in connection with the second 

 region we find that several of the Jamaican species are of importance 

 on account of their direct resemblance to others occurring on the 

 more immediate Pacific border of America. I have lately found 

 Sagartia nivca (Lesson, non Gosse, 1860)^ in some abundance on 

 mangrove roots in Kingston Harbour, while the only other known 

 localities are Paita and Callao, Peru. A new Jamaican EjjizoantMts, 

 living on Pinna shells, can scarcely be distinguished from E. humilis, 

 Verr., occurring at Panama. The genus Asteractis has known repre- 

 sentatives only at Panama and Jamaica. Also with many others of 

 the species given by Verrill from around Panama and Peru, there is 

 not the slightest doubt that when they come to be more thoroughly 

 and anatomically examined they will be found to show a closer agree- 

 ment with Caribbean forms than a present comparison will permit. 

 The West Indian Actiniaria, as was first demonstrated by McMurrich 

 on more general grounds, undoubtedly offer in detail additional 

 evidence in favour of a past communication between the Atlantic 

 and Pacific Oceans across what is now the Isthmus of Panama. 

 This conclusion * but supports the results already arrived at by in- 

 vestigators in other groups ; by Dr Giinther from his study of the 

 fishes ; by various workers on the marine Mollusca, the Crustacea, 

 and the Holothurians. Wiiile, as the pages of Natural Science have 

 revealed for some time back, the continuity or discontinuity of the 

 two Americas appears to be necessary for the solution of many of 



1 Jamaican waters contain at least seven species of Sagartids, and four Bunodidae. 

 ^ Histological examination shows that it will have to be removed from its present 

 genus. 



