446 PROCEEDINGS OF THE NATIONAL MUSEUM vol. loi 



our incomplete knowledge of the actinians of the east side of 

 Central America, the comparison given below is, of course, in- 

 complete and defective. 



The genera occurring in warm water in western America but 

 not in the Gulf of Mexico or Caribbean Sea are Calamactis, Phia- 

 loba, Isometridium, Nemanthus, Alicia, Epiactis, Phymactis (pro- 

 vided Cystiactis koellikcri described from West Indian waters by 

 Pax in 1910, p. 180, is not a Phymactis) , Gyrostoma (the single 

 small specimen from the West Indies described as a Gyrostoma by 

 Pax (1910, p. 176) is very doubtful and probably a very young 

 Actinia as Pax first suspected), Aiptasiomorpha, Botruanthus, 

 Isaracnanthus, and Pachycerianthus. 



The genera inhabiting the waters of the Gulf of Mexico and 

 West India but not, so far as we know at present, the districts of 

 Baja California to Peru are: All Corallimorpharia, Edwardsia, 

 Isoedwardsia, Bunodeopsis, Lebrunia, Actinia, Anemonia, Con- 

 dylactis, Actinoporus, Stoichactis, Homostichanthus, Phymanthus, 

 Isaurus, and Parazoanthus. 



The west and east sides of Central America have the following 

 genera in common : Anthopleura, Bunodosoma, Bunodactis, 

 Phyllactis, Telmatactis, Anthothoe {Actinothoe) , Zoanthus, Paly- 

 thoa, and Epizoanthus. 



As we can see, there is a great difference between the actinian 

 fauna on the west and east sides of Central America. That the 

 Corallimorpharia, apart from the genus Corynactis, and the gen- 

 era Lehrunia, Actinoporus, Stoichactis, Homostichanthus, Phyynan- 

 thus, Bunodeopsis, and Isaurus which, as a rule, are inhabitant 

 on coral reefs, do not occur on the west side is an easily explained 

 fact, because reef -constituent corals, though occurring, do not form 

 actual reefs there. It is curious, however, that there is no account 

 of Corynactis on the west side, though species of it live in Cali- 

 fornia and in Chile, but it is possible that the genus exists in the 

 lower littoral zone. Moreover, it is very probable that Edivardsia 

 appears on the west side, as the species of this genus are dis- 

 tributed in all oceans. The same probably is also true of Isoed- 

 wardsia. It is peculiar that Actinia, Anemonia, and Condylactis, 

 which live in many other localities than on coral reefs, have not 

 been discovered on the west side. 



As to the genera that are common between the west and the 

 east sides, Anthopleura, Bunodactis, Telmatactis, Actinothoe and 

 Anthothoe, Zoanthus, Palythoa, and Epizoanthus, they are so 

 widely distributed in warmer waters that we cannot conclude that 

 the actinian fauna of these districts are nearly related to each 



