336 PROCEEDINGS OF THE ACADEMY OF [1890. 



of the Pacific arise upon the western coast of America,' and flow- 

 ing through the islands of Polynesia and the East Indies distrib- 

 ute their species westward, and it would be naturally supposed 

 that the species occupying the area where the currents arise would 

 be also carried in that direction. This, however, is not so ; probably 

 for two reasons. 1. The equatorial counter-current impinges upon 

 the greater portion of the western coast of Central America and 

 produces a quiet area in which there is apparently little circulatory 

 motion. Further, the north and south equatorial currents arise 

 respectively off the coasts of Lower California and Peru, and prob- 

 ably come little into contact with the littoral fauna of west Central 

 America. 2. The eastern portion of the Pacific Ocean contains very 

 few islands which could serve as connecting points in the distribu- 

 tion of littoral forms. These are probably the reasons why the west 

 Central American forms are not found in the Indo-Pacific region. 

 The equatorial counter-current, which could form the only possible 

 means of communication from the Indo-Pacific tropical region to the 

 west Central American tropical region, traverses a tract in which 

 there are only a few scattered islands which are jDrobably not sufficient 

 in number to bring about the introduction of the fauna of the one re- 

 gion into the other. 



General Literature of the Echinoderm Fauna of the 

 West Indian Region (not including the Crinoids). 



1825. Thomas Say. On the species of the Linnsean genus Asterias 

 inhabiting the Coast of the United States. Jour. Acad. Nat. 

 Sci. Phila. (1), Vol. 5, p. 141. 



1826. Thomas Say. On the species of Linnsean genus Echinus in- 

 habiting the Coast of the United States. Ibid, p. 225. 



1851. L. F. Pourtales. On the Holothurite of the Atlantic Coast 

 of the United States. Proc. Anier. Assoc, 1851, p, 5. 



1856. Chr. Liitken. Contributions to the Knowledge of the Ser- 

 pent-Stars. II. Review of the West Indian Ophiurans. Vid- 

 ensk. Meddel. Kjobenhavn, p. 1. 



1859. Chr. Liitken. Contributions to the Knowledge of the Star- 

 fishes of the Coasts of Central and South America. Vidensk. 

 Meddel. Kjobenhavn, p. 25. 



1859. Chr. Liitken. Addimenta ad historiam ophiuridarum. II. 

 Description of little known Serpent-Stars from the West Indies 



1 See Dr. Van Bebber, Lehrbuch der Meteorologie, Stuttgart, 1890, Tab. ii. 



