GULF OF MEXICO 



269 



Indian western Pacific regions have liad this 

 origin, there is no reason to doubt that the 

 Isthmus of Panama was crossed about the same 

 time by the same species, or some of them. The 

 species that are perhaps most likely to have spread 

 so widely and to have crossed modern land bar- 

 riers so freely are now truly pan-tropical species, 

 but the evidence they provide, according to the 

 conventional canons of biogeography, is ruled 

 invalid by the possibility that they are spreading 

 today. Unhappily, if one chooses to follow the 

 rules and exclude the pan-tropical species, it can 

 only be said that the remaining species prove 

 nothing, at least as far as hydroids are concerned. 

 The reason is not so much biogeographic as 

 taxonomic. 



The number of hydroids common to the two 

 sides of Central America is large, but an even 

 larger number is common to th^ two coasts of 

 North America taken as a whole. According to 

 Eraser's tabulation (1944), 123 species are known 

 from east and west coasts of the Americas, and by 

 no means all of these are circumpolar. Neither 

 are the tropical species all pan-tropical. The 

 "American" distribution pattern is far too com- 

 mon to be accidental, but its commonness raises 

 doubts about the taxonomy. Fraser was a sound, 

 careful worker with a "good eye" for specific 

 differences. However, his experience, though 

 enormous, was largely confined to the Americas. 

 When one remembers that the hydroids of the 

 East Indies are poorly known (only tlrree families 

 of the Siboga hydroids having beea reported by 

 Billard before his death), one cannot escape the 

 suspicion that many species apparently endemic 

 to the American tropics are still to be collected, 

 or are already known under other names, from 

 other parts of the world. Apart from this tax- 

 onomic difficulty, inadequate knowledge of the 

 hydroids of the western Pacific and Indian Oceans 

 imposes another limitation on the case for Tethyan 

 paleogeography, for western Atlantic-western 

 Pacific disjunctions have often been used (however 

 unwisely) in building such a case, and we know 

 of no certain examples among hydroids. 



Until the hydroids of the world have been given 

 much more study and some monographic revision, 

 then, it is unsafe to use them for many zooge- 

 ographic purposes. 



CHECK LIST OF GULF OF MEXICO 

 HYDROIDS 



Geographic distribution is indicated by the 

 following symbols: 



K, Florida Keys, including Cay Sal Bank and 

 southern Florida as far east as Miami, but not 

 the Bahamas. 



T, Tortugas. 



C, Cuba. 



Y, Yucatan. 



NW, northwestern Gulf (Texas, Louisiana). 



NE, northeastern Gulf (including Tampa Bay). 



Ca, Caribbean Sea. 



EP, eastern tropical Pacific Ocean, south of 

 United States-Mexico boundary, and including 

 the oceanic islands. 



*, starred names are new records for the Gulf of 

 Mexico, found in the Woods Hole Oceanographic 

 Institution fouling collection. 



Suborder Gymnoblastea (Anthomedusae), 

 athecate hydroids 



Cordylophora lacustris Allman, 1844. NW; Ca. 

 Turritopsis fascicularis FT&seT, 1943. K. 

 *Turritopsis nulricula McCrady, 1856. K; Ca, EP. 

 Syncoryne eximia ' (Allman, 1859). NW. 

 Syncoryne mirabilis L. (Agassiz), 1862. K; EP. 

 Zanclea costala Gegenbaur, 1856. T, NW; Ca, EP. 

 Zanclea gemmosa McCrady, 1858. T; EP. 

 Bimeria franciscana Torrey, 1902. NW; B. 

 Bimeria humilis Allman, 1877. T, NW; Ca. 

 BougainvUlia carolinensis (McCrady, 1858). T, NW. 

 Bougainvillia inaequalis Fraser, 1944. NW. 

 BougainvUlia rugosa Clarke, 1882. NW; Ca. 

 Eudendrium album Nutting, 1898. K; EP. 

 Eudendrium allenualum Allman 1877. T; EP. 

 Eudendrium carneum Clarke, 1882. T; Ca, EP. 

 Eudendrium distichum Clarke, 1879. K. 

 Eudendrium eiiguum Allman, 1877. K; Ca, EP. 

 Eudendrium eiimium Allman, 1877. K, NE; EP. 

 Eudendrium fruticosutti A\lma,n, 1877. K. 

 Eudendrium gracile ■\llman, 1877. K. 

 Eudendrium hargitti Congdon, 1906. T. 

 Eudendrium laxum Allman, 1877. K; Ca. 

 Eudendrium speciosum Fraser, 1945. NE. 

 Eudendrium tenellum Allman, 1877. K; Ca, EP. 

 Eudendrium tenue A. Agassiz, 1865. NW?; Ca, EP. 

 H ydraclinia echinala Fleming, 1828. K, NW. 

 Podocoryne carnea Sars, 1846. NW. 

 Pennaria liarella (Ayres, 1854). K, T, C; Ca, EP. 



' N. J. Berrill, in a letter to the author, has given good reasons for suspect- 

 ing that the species reported under this name from Texas and from western 

 Florida (Deevey 1950), is an undescribed species. 



