310 MINERALS AND GEOLOGY 



The other portions of this district, extending to the Ottawa river, 

 are occupied by Lower Silurian formations. The first of these in 

 ascending order, the Chazy formation, is made up principally of 

 light-coloured, thin-bedded sandstones, followed in places by grey or 

 dark-brown limestones largely employed in the manufacture of hy- 

 draulic cement or " water-lime." In these limestones, examples of 

 the ostracod Leperditia Canadensis (fig. 165), or a closely allied 

 species, are especially numerous. The brachiopod Rhynconella plena 

 (fig. 190) is also very characteristic, and examples occur in great pro- 

 fusion throughout most of the Chazy strata. Camerella varians 

 (fig. 192) is another characteristic Chazy type. Many other brachi- 

 opods, with Illenus globosus (fig. 170) and other trilobites, and 

 numerous gasteropods (Murchisonia, Pleurotomaria, etc.) are of 

 common occurrence in these strata. In outlying patches on the 

 gneissoid rocks near Pembroke, etc., in Renfrew, some of the lower 

 Chazy beds contain small nodular masses of a dark-brown colour, 

 regarded as fish-coprolites. They consist of impure phosphate of 

 lime mixed with shells of lingulse in a fragmentary condition. In 

 these beds also examples of Lingula Lyelli (fig. 205) and pleuroto- 

 marise are abundant. Good exposures of the Chazy formation, 

 generally, occur elsewhere at L'Orignal and Hawkesbury on the lower 

 Ottawa, and at various points in Lochiel, Cornwall, Nepean, Huntly, 

 and adjacent townships. 



The Chazy beds are succeeded by Black River and Trenton strata, 

 mostly represented by very fossiliferous limestones of a dark grey 

 colour. These occur in force about Ottawa City, as well as in Cum- 

 berland township, and throughout the Counties of Russell, Stormont, 

 and Carleton, generally. Among the more typical fossils, the follow- 

 ing may be especially cited: Glyptocrinus decadactylus (fig. 154), 

 Lecanocrinus elegans, and other crinoids, mostly however in the form 

 of stem fragments; many cystideans as Glyptocystites Logani, etc., 

 (fig. 158); Hemicystites Billingsii (fig. 161); numerous brachiopods, 

 as Strophomena alternata (fig. 194), Orthis testudinaria (fig. 191); 

 various species of modiolopsis and other lamellibranchiates ; numerous 

 gasteropods, as Maclurea Logani (fig. 222), Pleurotomaria Progne 

 (fig. 219), Subulites elongatus (fig. 225), and others; various ortho- 

 ceratites; and several trilobites, more especially Asaphus platycephalus 

 (fig. 168), Cheirurus pleurexanthemus (fig. 173), and Trinncleus con- 



