434 



SCIENCE. 



[N. S. Vol. XVII. No. 428. 



use to some of your readers. I, therefore, 

 give exact reference. 



At the session in ' Thermidor, an 11 de 

 la Eepublique' (1803), 'K Geoffroy' [Saint 

 Hillaire] presented an ' Extrait des observa- 

 tions anatomiques de M. Home, sur I'echidne,' 

 which was published in the Bulletin des Sci- 

 ences de la Societe Philomathique (Tome 

 III., p. 225-227— misprinted 125-127— pi. 14r- 

 16). In this communication Geoffroy re- 

 marks that ' Ornithorhincus' (Ornithorhyn- 

 chus) and Echidna, though closely related, 

 are generically distinct, but should be united 

 in the same order (_' ordre'). He reasons as 

 follows : 



" Mais, cependant, comme il est demontre, 

 par la dissertation de M. Home, que ces deux 

 genres s'appartiennent par un assez grand 

 nombre de rapports, je les reunis dans le meme 

 ordre, sous le nom Monoteemes, avee le car- 

 actere indicateur suivant: Doigts onguicules; 

 point de veritaMes dents; un cloaque commun, 

 versant a I'exterieur par une seule issue." 



In this article was also published the name 

 Echidna setosa, as is well known. 



Eafinesque, in 1815, in the ' Analyse de la 

 Nature' (p. 57), gave the Latin form Mono- 

 tremia to the word, adopting it for his ' 16 

 f amille ' of mammals. Theo. Gill. 



Cosmos Club. 



CURRENT NOTES ON PHY8I0GRAP3Y. 



OVERTHRUST MOUNTAINS OF NORTHERN MONTANA. 



The physiographic features that are asso- 

 ciated with various stages of dissection of 

 uplifted, folded or faulted structures are 

 coming to be fairly well known; but the fea- 

 tures resulting from the dissection of over- 

 thrust masses have as yet hardly gained recog- 

 nition in systematic physiography. Hence 

 the importance that attaches to certain pas- 

 sages in an account by Willis of the ' Stratig- 

 raphy and Structure, Lewis and Livingston 

 ranges, Montana ' (Bull. Geol. 8oc. Amer., 

 XIIL, 1902, 305-352), where a great over- 

 thrust has carried a heavy and resistant series 

 of nearly horizontal Algonkian strata more 

 than seven miles eastward over the previ- 

 ously warped Cretaceous strata of the plains. 

 The overthrust mass is now greatly denuded; 

 castellated outliers and promontories stand 



forward between large embayments, and the 

 embayments are drained eastward over the 

 plains as if the original drainage of the over- 

 thrust mass (presumably westward) had been 

 destroyed by the retrogression of the over- 

 thrust escarpment. Before the overthrust 

 took place, the relatively weak strata of the 

 plains had been worn down to a peneplain; 

 and it is believed that the Algonkian strata 

 further west had at the same time been re- 

 duced to moderate relief. The general up- 

 lift associated with the overthrust exposed 

 the plains to dissection, but remnants of their 

 peneplain phase are still well preserved. The 

 more active uplift of the overthrust raised 

 the Algonkian strata to. mountain height and 

 allowed their deep dissection, but back of the 

 Front ranges the subdued forms of the earlier 

 cycle are still more or less preserved in the 

 mountainous uplands at heights of 7,500 feet, 

 where the general profile is independent of 

 structure. In the front ranges, where the 

 mountains rise to heights of 9,000 and 10,000 

 feet, revived erosion, by both water and ice, 

 has caused so great a dissection that no trace 

 is to be seen of whatever subdued forms may 

 have existed before uplift. Here the very 

 general association of the higher summits 

 with anticlinal belts, and of the intermediate 

 longitudinal valley with a shallow synclinal 

 belt, suggests corrugation at as late a date as 

 that of the overthrust by which the general 

 uplift was produced. Strong erosion by 

 heavy valley glaciers is inferred in the Front 

 ranges, where high-cliffed amphitheatres hold- 

 ing lake basins are characteristic features. 

 One of the most notable peculiarities of the 

 district is the location of the continental di- 

 vide at the eastern base of the mountains, 

 where a branch of Flathead river (Columbia 

 system) rises at the very margin of the plains 

 in the pass that is followed by the Great 

 Northern Railroad. 



THE OASES OF SOUP AND m'ZAB. 



The dual character of geography is seldom 

 better represented than in a study by Brunhes 

 on ' Les oasis du Souf et du M'zab comme 

 types d'etablissements humains ' {La Geogr., 

 v., 1902, 5-20, 175-195) ; that is, the physio- 

 graphic environment and the organic response 



