,89.. NOTES AND COMMENTS. 165 



when the nests were disturbed the mites, being slow of foot, leaped 

 on to the head of a passing ant, and were borne off to a place of 

 safety. The ants appeared to have not the slightest objection to this 

 familiarity on the part of their guests ; on the contrary, indeed, for 

 they carried off the mites without making the least attempt to dislodge 

 their riders, and ants are not as a rule the most peacefully disposed 

 of animals. In the case of another species of ant, the care taken of 

 the Gamasids was even more remarkable. When danger threatened 

 the colony, the ants carried off both the mites and their young, just 

 as they carry off their own young. After a careful series of experi- 

 ments, Mr. Michael comes to the conclusion that the mites repay 

 the hospitality shown to them by removing the bodies of deceased 

 ants, which they utilise as food. 



South American Extinct Mammalia. 



In a recent issue of the Anales d. Mus. Nat., Buenos Aires, '^ Dr. 

 Hermann Burmeister continues his important researches on the 

 fossil mammals of Argentina. Dr. Burmeister is one of those 

 designated under the somewhat inelegant title of " lumpers " ; and, 

 although he may perhaps err somewhat in the opposite direction, he 

 is certainly doing good work in calling attention to the reckless 

 manner in which so-called genera and species have been named by 

 some of his fellow-workers. Indeed, when, according to their own 

 showing, no less than five genera, to say nothing of species, have been 

 manufactured by the latter out of remains belonging to Nesodon im- 

 bricatus and A'^. ovinus, while Dr. Burmeister adds three more to the 

 list, it is high time that something were done to check this endless 

 flow of names— names in many cases no sooner published by one writer 

 than they are relegated to the rank of synonyms by another. In addi- 

 tion to showing the absolute invalidity of some of these names by 

 actual comparison of the specimens on which they were founded, our 

 author in other cases shows that for physical reasons it would be an 

 absolute impossibility for such a number of gigantic animals as have 

 been named to exist within the limits of the country. 



A large portion of the memoir is devoted to a description of the 

 Ungulate genus Nesodon, a near ally of the huge Toxodon ; but we have 

 also notices of other interesting forms. Among these is the occurrence 

 of a species of the Edentate genus Megalonyx (as typified by M. jeffer- 

 soni, of Kentucky) in the Tertiaries of South America, which is a point 

 of considerable interest in distribution. Not less important from 

 another aspect is Dr. Burmeister's statement that the alleged occur- 

 rence of enamel in the teeth of certain of the Ground Sloths of the 

 Lower Tertiaries of Argentina is due to osteo-dentine having been mis- 

 taken for enamel. By this we have at a single stroke the genera Pro- 

 megatherium and Promylodon severally united with Megatherium and 



1 Vol. iii., pp. 401-4S8, pis. viii.-x. (1891). 



