48 The Ottawa Naturalist. [June-July 



how important the algae are as reef-building organisms to-day, 

 and remarks that Lithothamnion-structure is easily obliterated 

 by percolating waters so as to form a structureless limestone. 

 He concludes: "It is freely admitted that in these pebble-like 

 structures from the Cambrian and Ordovician limestones, no 

 organic structure has been found sufficiently well preserved to 

 prove conclusively that they are of algal origin, but their simi- 

 larity to such structures now forming is very suggestive." In 

 discussing the orientation of the edgewise conglomerates, he 

 follows Hahn's and Grabau's theory that the deformation and 

 regrouping is largely due to "submarine slumping." The " Stre- 

 phochetal conglomerates" mentioned by Seeley (9) are probably 

 not true conglomerates. Seeley writes (op. cit. p. 152): "The 

 spherical or elongated masses breaking down from a weathering 

 rock appear like rolled fragments or calcareous concretions, and 

 such without doubt they are in many cases. Yet a careful study 

 of these will disclose the fact that a portion of these nodular 

 forms have definite structure." Thus, the stratigrapher is apt 

 to be led astray by certain fossiliferous rocks, which, upon a 

 macroscopic and hasty examination, have all the earmarks of a 

 true intraformational conglomerate, but which really owe their 

 structure to a certain type of organism included in them. It 

 is possible, however, that true intraformational conglomerates 

 may be formed by the activities of organisms. The writer col- 

 lected an interesting specimen from the lower Beekmantown at 

 Bellefonte, which would seem to suggest another mode of origin, 

 but somewhat along the lines suggested by Brown. The speci- 

 men shows a narrow band of unstratified and peculiarly shaped 

 phenoclasts (see fig. 2). The phenoclasts themselves are only 

 slightly fossiliferous and are fine-grained, showing no definite 

 crystal structure, and have peculiar and varied outlines. The 

 interstices are filled with a cement largely composed of algae 

 and the debris of small shells, the former preponderating. 

 The shape of the phenoclasts and the presence of the algae in 

 the cement would seem to show that the fine-grained, un- 

 crystallized muds deposited in intermittent layers upon the sea 

 floor were broken while still in a plastic state by the action of 

 the algae. The processes of primary deposition of the limy mud, 

 floculation, and redisposition of the "conglomerate mass" were 

 practically coterminous with the primary lithification of the 

 limestone under discussion. Sardeson (10) in discussing the 

 pseudo-brecciated structure of the Ordovician limestones of 

 Manitoba, originally described by Wallace (11), makes the fol- 

 lowing statement : "In the bed number 3, lumps, cakes and lenses 

 of pure, light-coloured, fine-grained limestone lie isolated in a 

 brown, fucoidal shale, and the evidence is then clear that the 



