Apkil 4, 1902.] 



SCIENCE. 



555 



an upper molar of E. impenitor has 17 cross 

 ridges and one oi E. columbi 21 or 22, while 

 the number of ridges in the lower molars are 

 respectively 18 and 22, this last being an esti- 

 mate owing to the lack of a perfect specimen 

 for comparison. In each case the molars 

 of E. columbi are smaller. Thus Leidy's spe- 

 cies may be considered as definitely estab- 

 lished. 



The mastodons are, as species go, in a 

 badly mixed condition, and even the status of 

 the abundant and widely distributed Mastodon 

 americanus is by no means so well defined as 

 one could wish. The last molar of this species 

 varies enormously not only in size, but in 

 proportions and character of the enamel, and 

 while the typical last molar has four cross 

 crests and a heel, there may be four cross 

 crests only, or five cross crests and a heel. 

 Moreover, while the enamel is usually quite 

 smooth, it is often more or less rugose, in 

 some instances being decidedly wrinkled, and 

 M. rugosideiis of Leidy is undoubtedly based 

 upon a tooth of this character. A fine series 

 of teeth obtained by Mr. W. H. Holmes at 

 Afton, Ind. Terr., shows the great range of 

 variation in the teeth of M. americanus. 



M. shepardi, once called ohscurus, from Cali- 

 fornia, is a good species, characterized by a 

 small narrow last molar and by the partial 

 interruption of the valleys on one side. The 

 true Mastodon ohscurus is a species founded 

 by Leidy on an imperfect last molar from 

 North Carolina, described and figured on 

 plate XXVII., figure 16, of the Extinct Mam- 

 malian Fauna of Dakota and Nebraska. This 

 species is so far definitely known from our 

 eastera coast from Florida to Maryland, and 

 the specimens described as M. floridanus must 

 be known as M. ohscurus. The writer pleads 

 guilty to having overlooked this when editing 

 Dr. Leidy's posthumous paper on fossil verte- 

 brates from the Alachua Clays. It is prob- 

 able that M. serridens of Cope is a slightly 

 aberrant fifth molar of M. ohscurus, although 

 it was decided otherwise in the memoir just 

 referred to. Dr. Leidy was perhaps over- 

 cautious in making new species, and described 

 no less than three mastodons under the name 

 of ohscurus. As an offset to this it may be 



said that there is reason to believe that Pro- 

 fessor Cope went to the opposite extreme of 

 describing one species under three names. 



Mastodon mirificus, with a last molar hav- 

 ing six much-wrinkled cross crests, is another 

 well-defined species, but there are several 

 others that are not at present well defined. 

 Among these is M'. proavus of Cope, which 

 he doubtfully separated from M. angustidens, 

 and may prove to be the same as M. ohscurus 

 (:^ floridanus) of Leidy. The writer has 

 never seen a tooth of mastodon from an 

 American locality that was not readily disr 

 tinguishable from the European M. angusti- 

 dens, and he ventures to doubt the occurrence 

 of this species in North America. 



M. prodiicfus Cope is another dubious species 

 and so is M. tropicus, whose teeth as figured 

 by Cope are indistinguishable from those of 

 M. ohscurus, while the figure of M. proavus 

 strongly suggests the true M. shepardi. That 

 one tooth has one more cross crest than the 

 other and is more pointed at the heel means 

 little, as just such differences are known to 

 exist in the last molars of M. americanus, 

 while the last molars of various mastodons 

 appear to be exceedingly variable. 



The identification of the species of masto- 

 dons from scattered teeth is, if not impossible, 

 at least extremely difficult, while the attempt 

 to identify species from figures is equally 

 unsatisfactory. Another question on which 

 light is needed is whether the presence of 

 lower tusks and a long symphysis to the lower 

 jaw is a specific or sexual character, or 

 whether it may not be specific in some cases 

 and merely indicative of sex in others ? There 

 are certainly specimens of mastodon jaws 

 with and without tusks whose molars are in- 

 distinguishable. It is to be hoped that the 

 time is not far distant when we may have 

 sufficient good material to place our species 

 of mastodons on a satisfactory basis. 



F. A. L. 



CURRENT NOTES ON METEOROLOGY. 



THE DUST STORM OF MARCH 9-12, 1901. 



The remarkable fall of dust which occurred 

 over Europe about a year ago has been noted 

 in ■ numerous short articles in various scien- 



