170 A. E. Verrill — Comparisons of (J oral Faunae. 



But if floating forms should escape from the western Bahamas 

 and pass directly into the full current of the Gulf Stream, where the 

 velocity is three to four miles an hour, a large part of the northward 

 journey could be made in a much shorter time. Then we may sup- 

 pose that by eastward surface currents, caused by the prevailing 

 southwest winds, such forms could easily be driven eastward from 

 the Gulf Stream to the Bermudas. By this course it is probable 

 that the journey might be made in less than four weeks, under 

 favorable conditions. 



That this course is taken by many forms of marine life is certain, 

 for after every period of strong southwesterly winds large numbers 

 of Gulf Stream species of animals are cast ashore on the Bermudas, 

 especially on the southern side. Among these are Physalia, the 

 Gulf-Stream crabs and shrimp, etc. 



Probably the larval period of many corals is too brief to permit 

 them to make this journey. Others may arrive there that are not 

 able to endure the low temperature of the water during the winter. 



Thus it happens that many of the West Indian genera and species 

 are not found at the Bermudas. 



The absence of all varieties of Acropora (Madrepora) muricata 

 is particularly noteworthy, for these are among the most abundant 

 and important of the West Indian reef corals. 



Other important West Indian genera that are lacking are Col- 

 pophyllia, Mceandrina (= Pectinia auth.), Dendrogyra, Die/to- 

 coenia, EusrniUia, Stephanoeosnia, and Solenastrcea. 



The absence of certain very common species of West Indian corals, 

 and the presence of others of the same genera, is also noteworthy. 

 Thus Mamndra clivosaand M. (Manicina auth.) areolata are absent, 

 while two other species are present in abundance. Agarieia agari- 

 cites is absent, while A. fragilis is common. Porites fureata is 

 unknown, while P. polymorpha (=r clavaria) and P. astreoides are 

 common. 



On the other hand, some genera and species appear to be more 

 abundant than in most parts of the West Indies. Thus the subgenus 

 Isophyttia, so abundant here, seems to be less developed elsewhere. 

 The same is perhaps true of Oevlina and Madracis, as well as of 

 Agarieia fragilis and Mceandra {Diploria) labyrinthiformis. The 

 latter is here the prevailing reef coral, but it seems to be relatively 

 less abundant in the West Indies. But ZMr. Whitfield informs me 

 that it is very abundant at the Bahamas. 



