NO. 2062. NEW ROTATORIA FROM PANAMA— EARRING. 561 



fauna of the Isthmus is South American. This is merely corrobora- 

 tive of the reports on other groups, which have established the agree- 

 ment of the Isthmian fauna in general with that of South America. 



The two lists record a total of 138 species, of which 35 are Hmited 

 to South and Central America. As both lists are fragmentary by 

 reason of the nearly complete absence of the illoricate species, a more 

 accurate judgment may be arrived at by a study of the genera Lecane 

 and Monostyla, in which all the species are recognizable, even when 

 contracted. A total of 43 species belonging to these two genera occur 

 in the combined lists, 21 of which are not known outside of the South 

 American faunal region and 26 species are known only from the Amer- 

 ican continent. Naturally both Murray's and this list have their quota 

 of rare species, but many of the exclusively South American species 

 are abundant, such as Lecane arcula, L. comjpta, L. crepida, L. curvi- 

 comis, L. Tiana, L. pusilla, Monostyla decipiens, M. furcata, M. pyri- 

 formis, M. rugosa, and M. virga. No doubt some of these will even- 

 tually be found elsewhere, but on the other hand it is at least equally 

 probable that many more undescribed species exist in South America, 

 in view of the limited territory represented by the collections, and 

 the conclusion that it is entirely proper to speak of a distinctly South 

 American rotatorian fauna seems therefore irresistible. 



The locaUzation of so many species of Rotatoria should go far to 

 disprove the importance of birds as agents of dissemination. No one 

 win of course deny that birds do influence distribution to some extent, 

 but it is extremely doubtful whether it amounts to more than equal- 

 izing the fauna of circumscribed locaUties. That any long-distance 

 transmission takes place is a purely gratuitous assumption; it is ren- 

 dered highly improbable, if not actually disproved, by the diversity 

 of the rotatorian faunas of North and South America. It is well 

 known that our migratory birds winter on the shores of the Caribbean 

 and countless millions make the trip every year, so that the rotatorian 

 fauna of America from the Equator to the Arctic Circle should be 

 sensibly uniform, if birds were even accidental carriers. The indi- 

 cated great diversity of the North and South American faunas flatly 

 contradicts this. 



While it has been frequently claimed that the Rotatoria are dis- 

 tributed aU over the world with something approaching monotonous 

 uniformity, the evidence upon which this assertion is based appears 

 entirely too fragmentary to draw any such far-reaching conclusions 

 from. And it would be necessary to bring forward irrefutable evi- 

 dence, as a uniform, cosmopolitan distribution is unknown in any 

 other subdivision of the animal world. It seems particularly out of 

 place in the case of the Rotatoria, as it is in direct opposition to the 

 better known facts of the distribution of the Entomostraca, which as 

 far as we know ought to be sensibly parallel, at least the adaptation 



34843°— Proc.N.M. vol.47— 14 36 



