12 THE HABITAT OF THE EURYPTERIDA 



middle part of the Belt Terrane in Montana. The remains are very 

 numerous, most of them being exceedingly thin films flattened in a 

 calcareous shale and showing no definite surf ace markings (288, 21). 

 Weller has collected specimens from the Altyn limestone at the type 

 locality north of Altyn in the valley of Swift Current Creek, Montana, 

 at the base of the Appekunny Mountains where the remains are 

 embedded in a fine calcarenyte matrix and show surface markings 

 (288, 40, pi. 7, fig. 4). Specimens have also been collected from the 

 Altyn limestone at about the same horizon near Johnson Creek on 

 The Continental Divide, Alberta, Canada. These show surface mark- 

 ings, and have been referred by Walcott to B. danai (288, 40, pi. 7, 

 figs. 2, 2a, 3). 



In a recent communication from Dr. Walcott, I have his state- 

 ment about the occurrence of the merostome remains in the different 

 sections. In the southeastern area of the Big Belt Mountains he 

 found a series of sandy shales and sandstones between the top of the 

 Newland limestone and the base of the Greyson; these carried Beltina. 

 In the sections in the Little Belt Mountains Walcott found it difficult 

 to determine whether the shales carrying Beltina belonged to the 

 Greyson or to the Newland. In the Northern Montana section the 

 merostome remains are found in the lower portion of the Altyn lime- 

 stone, so that, concludes Walcott, "the correlation on the basis of 

 fossil evidence is that the Greyson and Altyn are about the same 

 age." 1 The fossils from the Altyn limestone were identified by 

 Walcott as Beltina danai, and Clarke and Ruedemann agree that the 

 fragments are remains of merostomes. They are, however, skeptical 

 about the correlation of the Altyn with the Belt terrane and they 

 are justified in this skepticism so long as the correlation is based upon 

 the fossils alone, for if the organic remains in the Belt terrane are not 

 eurypterids and are not the same as those in the Altyn, then the 

 correlation is unfounded. Furthermore, the palaeontological evi- 

 dence alone would not be sufficient for correlation, and, if, as I believe, 

 these Pre-Cambric formations are to be regarded as of continental 

 origin, then neither physical nor faunal data will lead to correlations, 

 since the same lithological successions will be repeated time and 

 again in different localities and in addition the synchroneity of river 

 faunas is difficult to establish. 



Thus at present it is impossible to say which authority is to be 

 accepted. Walcott plans to do more work on these sections in the 



1 Dated February 26, 1915. 



