OKIGIN OF ROCK-SALT. 421 



number of these animals — as also of the previous order — have been 

 found in the Karoo beds of South Africa, and described by Prof. Owen. 



Birds. — No birds have yet been found in the strata of the Triassic 

 age, unless we except the so-called bird-tracks of the sandstone of 

 the Connecticut Valley and elsewhere, which we will discuss further 

 on. 



Mammals. — Remains of two or three small insectivorous Marsupials 

 have been found in the uppermost Triassic, both of Europe and of the 

 United States. Figures of a tooth of one of these, Microlestes anti- 

 quus, are given (Fig 625). The remains of the mammals of the 

 Triassic are so few and fragment- 

 ary that it is difficult to make out gapjjfW <jffVw ifift 



their affinities, but it is probable J/fSsrl jw"SS t cHl d 03331k 



7 L fW/ih i 1IA ( ') - ■---■■■If ^S^^gy 



that they were a generalized type fP|i|I KfV'l if! 



connecting marsupials with the ^^^^^ili mn/^ W 



.--i-i -i , -i -i >i Fig. 625. — Tooth of the Microlestes antiquus. 



still lower monotremes and both 



with Theriodont Reptiles. But as these are found in very small num- 

 ber sand only in the uppermost Triassic beds, and as similar animals are 

 found in much greater numbers in the Jurassic, it seems best to regard 

 these as anticipations, and to put off the further discussion of the affini- 

 ties of the earliest mammals until we take up that period. 



Mammals probably preceded Birds. This is not a little remarkable. 

 But it must be remembered that Birds are very closely allied to Rep- 

 tiles, and may be regarded as a secondary offshoot of the reptilian 

 branch. 



Origin of Rock-Salt. 



Neither rock-salt nor coal is confined to the rocks of any particular 

 age. Both have been formed in every age ; both are forming now. 

 But as the subject of the origin of coal-deposits was discussed in con- 

 nection with that age during which it was accumulated in the greatest 

 abundance — the Carboniferous — so the origin of rock-salt is best dis- 

 cussed in connection with the so-called Saliferous or Triassic. 



Age of Rock-Salt. — As already stated, rock-salt is found in strata 

 of all ages, and is forming now. Moreover, there is no period which 

 deserves the name Saliferous to the same extent that the Carboniferous 

 deserves its name. The salt of Syracuse, New York, is found in the 

 Upper Silurian ; that of Canada, which exists in immense beds 100 

 feet thick, is found in the Upper Silurian or Lower Devonian ; that of 

 Pennsylvania is Upper Devonian ; of Southwest Virginia is sub-Car- 

 boniferous ; that recently discovered in Kansas is in the Trias ; * that 

 of Petite Anse, Louisiana, is uppermost Cretaceous or lowest Tertiary 

 (Hilgard). In Europe, the English salt-beds are Triassic, the German 



* Hay, American Geologist, vol. v, p. 65, 1890. 



