334 GEOLOGY OF THE BLACK HILLS. 



times slightly curved ; still they give no evidence of bifurcating or anas- 

 tomosing with each other, as is the case with Scolithus linearis. In these 

 features they differ from that genus, and we are strongly inclined to consider 

 them as having had quite a different origin. It has been suggested that 

 they might have been the perforations or sheaths of the peduncles of lin- 

 guloid shells, and the same suggestion was made by the writer some years 

 ago to Professor Morse concerning some perforations in the sandstones of 

 the same formation at Trempeleau, Wis. ; but in this latter case the tubes 

 are often found surrounded, or lined, by the fragmentary shells of Lingulas, 

 and the sandstones contain on their surfaces shells of Lingula or Obolella ; 

 but these specimens furnish no such remains, nor are there any such brought 

 from the localities from which these tube-bearing specimens were obtained. 

 This fact would be rather against their linguloid origin, although they seem 

 to be all vertical to the bedding of the rock. This latter feature, together 

 with their rigid and somewhat uniform character, leads us to consider them 

 as the burrows of some species of Annelid, rather than the cavities left by 

 the removal of the remains of plants.* Another block of sandstone from 

 Custer Peak, near the central portion of the Black Hills, has vertical tubes 

 of a similar form, but of larger size ; while a block of reddish sandstone, 

 from the head of Redwater Canon, is filled with irregular cavities of vari- 

 ous sizes and shapes, being neither uniform in size or position, but which 

 have all the appearance of broken drifted stems of plants. These latter, 

 coming from the same locality as the species of Cruziana contained in the 

 collection, it is more natural to suppose may be the remains of vegetable 

 organisms. These latter specimens are exactly similar to those figured by 

 Dr. D. D. Owen in the Geological Report of Wisconsin, Iowa, and Minnesota, 

 Plate 1 C 1 , Figs. 1-8. 



* Since writing the above I have seen and described, in the Geological Report of Wisconsin, 

 specimens of a similar form that present indisputable evidence of their annelid character. 



