230 THE CAMBRIAN. [bull. 81? 



in 1851. He described its mode of occurrence and stratigraphic posi- 

 tion. 1 This paper was followed by one by Prof. Owen, who refers the 

 tracks to a species of tortoise.* 2 



At a meeting of the British Association for the Advancement of 

 Science, held at Ipswich iu 1851, Sir W. B. Logan exhibited a slab of 

 sandstone and a cast from a larger one, showing what Prof. Owen had, 

 in a communication to the Geological Society, pronounced to be a track 

 and footsteps of a species of tortoise, thus proving the existence of 

 reptiles at the very earliest period of known animal life. 3 



In describing in 1852 the sandstone occurring in Beauharnois County, 

 Canada, Sir W. E. Logan makes the following observation upon Sco- 

 lithus linearis : 4 



In this part it [the sandstone] is abundantly marked over considerable surfaces by 

 what the geologists of New York have called Scolithus linearis, which consists, where 

 tho rock is weathered, of straight, vertical cylindrical holes, of about an eighth of an 

 inch in diameter, descending several inches, and where the rock is unweathered of 

 corresponding solid cylinders, composed apparently of grains of sand, cemented by 

 a slightly calcareous matrix, more or less tinged with peroxide of iron. Mr. Hall 

 and other American geologists include them among the Fucoids of the rock, but they 

 appear to me more like worm holes. In one or two instances I have perceived that 

 the tubes are interrupted in their upward course by a thin layer of sand, of a por- 

 tion which descends into them and stops them up ; and from this it would appear 

 that the cylinders were hollow when tho superincumbent sand was spread over them. 

 Whatever may be the origin of the tubes, they strongly mark many beds in the upper 

 part of the sandstone throughout tho Canadian portions of its distribution already 

 mentioned; and it is stated by Mr. ITall that the same characteristic accompanies 

 the Potsdam sandstone in New York and Pennsylvania and as far as Tennessee. 



He also speaks of the presence of Fucoides and of Lingula antiqua. 

 This is followed by a detailed account of the strata containing the foot- 

 prints described in the same volume by Prof. Owen. 



This paper by Mr. Logan was followed by one by Prof. Owen, who 



described the various footprints and impressions under the following 



names : 5 



Protichnites septem-notatns, p. 214. 

 Protichnites octo-notatus, p. 217. 



latus, p. 218. 



multinotatus. p. 219. 



lineatus, p. 220. 



alternans, p. 221. 



The descriptions are accompanied by admirable illustrations of the 

 varieties designated. He concludes that the impressions appear to have 

 been made by animals allied to Limulus. 6 



1 On the occurrence of a track and footprints of an animal in the Potsdam sandstone of Lower 

 Canada. Quart. Jour. Geol. Soc, London, vol. 7, 1851, pp. 247-250. 



2 Ibid., p. 250-252. 



3 On tho age of the copper-bearing rocks of Lake Superior and Huron, etc. British Assoc, Rep. 

 Trans., of sections for 1851-52, p. 62. 



* On the footprints occurring in tho Potsdam sandstone of Canada. Quart. Jour. Geol. Soc. Lond., 

 Proa. vol. 8, 1852, pp. 200, 201. 



6 Description of the impressions and footprints of the Protichnites from the Potsdam sandstone of 

 C:»nada. Quirt. Jour. Geol. Soc. London, vol.8, 1852, pp. 214-225. 



t Op.cit,,p.224. 



