246 CONFERENCE ON PALEOZOIC PALEOGEOGRAPHY 



their remains, did not possess the massive facies of the typical reef- 

 builders; it may, therefore, be unsafe to make from biologic data a de- 

 duction applying to them. But some information is furnished by the 

 nature of the sediments in which they are embedded. Walcott® gives 

 the following localities for the species : Silver Peak, Nevada ; Straits of 

 Belle Isle, Labrador, and conglomerate limestone east of Troy and 

 Schoolhouse No. 8, Washington County, New York. In the Silver 

 Peak section the Arcliwocyathince occur in a limestone and silico-argilla- 

 ceous shale in association with Olenellus gilherti; in the Straits of Belle 

 Isle, in gray, reddish, and greenish limestones, there occur the character- 

 istic coral-reef limestones varying in thickness from 25 to 50 feet; east 

 of Troy, New York, in a brecciated limestone showing evidences of wear 

 in most instances. Walcott says: 



"The arenaceous beds (with ripple marks and trails) of the western 

 Nevada-California area and the interformational conglomerates of eastern 

 New York proves the presence in both areas of relatively shallow water."* 



We can therefore safely say that some Archceocyathince lived in shoal 

 water, and, as they formed considerable accumulations of calcium car- 

 bonate, they probably lived in a warm sea. Eegarding the oceanic tem- 

 perature of the Lower Cambrian, Walcott says, in the article already 

 cited : 



"That more or less uniform and favorable, even warm, climatic conditions 

 must be appealed to in explanation of the widespread occurrence of almost 

 identical coral-like organisms in the Lower Cambrian and of the vast number 

 of individuals of various species of trilobites, etcetera, in Middle Cambrian 

 time." 



In the Upper Cambrian the Stromatoporoid Cryptozoon obtained a 

 great development, and continued into the basal Ordovician. This 

 Hydrozoan formed spherical masses from 1 to 2 feet in diameter, or 

 formed greatly expanded plates a foot or more thick and from 5 to 100 

 feet in horizontal extent. 



The Eugosa are represented in the Middle Ordovician by Columnaria; 

 the Alcyonaria, represented by Halysites, Heliolites, etcetera, soon ap- 

 pear, and the great coral reef-builders of Paleozoic time were initiated. 

 These reefs are formed by the Hydroids, Stromato cerium, Stromatopora, 

 Beatricia, Lahechia, etcetera; the Alcyonafian, Halysites, Heliopora, 

 etcetera; Favosites and its allies; a great profusion of Eugosa, includ- 

 ing many genera of massive facies, as Columnaria, Eridophyllum, Cya- 



8 Tenth Ann. Rept. U. S. Geol. Survey, 1890 ; BuH. U. S. Geol. Survey, No. 30, 1886. 

 ^ Outlines of geologic liistory, with especial reference to North America. Symposium 

 organized by Bailey Willis, p. 35. 



