284 bulletin: museum of comparative zoology. 



tral America" (Proc. Acad. Nat. Sci. Phila., 1908, 60), says that the 

 actual distribution of the Odonata is determined by the conditions under 

 which their aquatic larvae are able to exist, and that our present information 

 refers to the appearance of the imagos in certain localities, and the sum- 

 mary herewith presented rests on the unproven assumption that the adults 

 do not wander far from the waters in which they have passed their earlier 

 stages or in which their offspring are capable of surviving. There are 

 about 91 species of Odonata known in the West Indies; 56 of these, or 

 61^ per cent, also occur in Central America. The number of species 

 common to both regions is likely to be increased by future explorations. 

 But making use of the present figures, it is very surprising that only 61^ 

 per cent of the West Indian Odonata are found in Mexico and Central 

 America, seeing that the prevalent winds on the east coast of the main- 

 land are easterly. With such insects as the Odonata one might expect 

 winds to play an important part as means of dispersal. 



Scharff quotes Mr. C. T. Simpson, who has had experience of oceanic 

 dispersal in the West Indian region. He has examined floating rafts of 

 bamboo, which would be suitable in the transportal of invertebrates, 

 nevertheless he does not attach much importance to this means of distribu- 

 tion. " The fact," he remarks, " that the operculates (operculate land- 

 shells) form so large a proportion of the Antillean land-snail fauna, that 

 a majority of the genera are found on two or more of the islands and the 

 mainland, while nearly every species is absolutely restricted to a single 

 island, appears to me to be very strong testimony in favour of a former 

 general land connection." 



Since the previous notes on the zoogeography were written, Dr. Scharff's 

 paper, " On an Early Tertiary Land-Connection between North and South 

 America " (Amer. Nat., 1909, 43, p. 513-531), has been received. While 

 this does not deal directly with the West Indies, nevertheless it contains 

 references and statements which leave no room for doubt but that Dr. 

 Scharff does not question the existence of an Antillean continent. His 

 quotation from Ortmann (Joe. cit., p. 518) is pertinent : "In place of the 

 present Southern continent he thinks that towards the end of Mesozoic 

 times, there existed the old Brazilian land (Archiplata), an Antillean 

 continent (including the West Indies and Venezuela) and also the Chilean 

 coast range." Again, in discussing Arldt's views, Dr. Scharff says : " His 

 conception of an extensive land having once flourished to the west of Cen- 

 tral America, while the latter was largely submerged, is not altogether 

 new. In alluding to the east-westward trend of the Antillean Cordillera 

 and its abrupt termination on the Pacific coast of Guatemala, Professor 



