1908] Notes o\ vSilitriax vS'iro.matoPokoids 25 



NOTES ON SILURIAN STROMATOPOROIDS FROM 



HUDSON'S BAY. 



Hv William A. Parks, Ph.D.. Associate Professor of 

 Geology, University of Toronto. 



Through the kindness of Dr. J. F. Whiteaves, the writer has 

 had the opportunity of examining a collection of Stromatopo- 

 roids obtained by Dr. Robert Bell, Dr. A. P. Low, and by Messrs. 

 Wilson, Dowling and 'Sullivan in the Silurian area to the 

 westward of James Bay. The exact locality of each specimen 

 will be found under the different species, iDut in general, it mav 

 be stated that the material was procured on the following 

 streams: Pagwachuan River, Equan River, Little Current 

 River, Attawapiskat River, and the Fawn Branch of the Severn, 

 also on Cormorant Lake. None of the material can be said to 

 l^e in a satisfactory condition, as the minute structure is, to a 

 great extent, destroy^ed by interstitial crystallization. Silicifica- 

 tion, so common in the Niagara horizon to the south of the 

 Height of Land, lias played but .small part in the fossilization 

 of these forms. The horizon indicated by the species found is, 

 for the most part, comparable with the upper beds of the Niagara, 

 t'Ut the extreme north of the region presents one species which 

 occurs only in the lower Niagara and in the Clinton of southern 

 Ontario. In association with some of the Stromat(jporoids, Dr. 

 Whiteaves finds Pycnostyhis giielphensis and P. elegans, typical 

 Guelph corals; but no Stromatoporoid exclusively Guelph 

 has been identified. With the exception of two new species, a 

 preliminary description of which is here gi\'en, all the forms are 

 reviewed in an article now in press (Niagara Stromatoporoids, 

 University of Toronto Studies, Geological Series, No. 5.) 



Clathrodictyon vesiculosum, Nick, and Murie. 

 This wide-spread and varied species is the commonest form 

 in the lower beds of the Niagara and in the Clinton of southern 

 Ontario and the ignited States, but only one example has been 

 identified from the present collection. This species is cliarac- 

 terized by very close-set laminae from, which the radial pillars 

 arise by minute inflections. The varying manner of this inflec- 

 tion results in different degrees of crumpling of the laminae 

 so that many varieties might be established, ranging from those 

 in which the laminae are practically straight and the pillars 

 independent, to those in which excessive crumpling has reduced 

 the interlaminar spaces to a series of vesicles, and rendered the 

 identification of the pillars as independent structures almost 

 impossible. To this latter type the specimen under review 



