Raymond: Thk Chazy Formation and its Fauna. 507 



Illccniis ^:;lobosiis, Pliomcrops canadensis, Bitcania sulcaiina, Kaphistoma 

 stai/iineii/ii and Isoteliis ohtiisiivi. 



Zone 3c. The Modiolopsis fa/ni/orfnis zone. 



In this zone Cainarota'chia plena is abundant almost to the cxcUision 

 of other species. The faunule extends to the top of the formation at 

 Chazy, Grand Isle, and Valcour Island. The characteristic fossils are 

 Camarota'chia plena and Modiolopsis falm/orniis. 



Canadian Exposures. 



North from Valcour Island and Chazy the various divisions cannot 

 be followed in the lists published, but this is due to the fact that no 

 sections have been carefully studied in that region. The various lists 

 published by the Canadian Survey and copied on the preceding pages 

 do show, however, that fossils characteristic of all three of the divi- 

 sions are found in that region. The Champlain Valley fauna is found 

 as far north as Joliette, 35 miles north of Montreal and about 85 miles 

 north of Chazy. To the west, it is found again at Hawkes- 

 t'ury, 75 miles in a straight line from Chazy and 55 miles from 

 Montreal, showing a considerable area through which the fauna is 

 distributed. 



West from Hawkesbury, a decided change in the fauna is found at 

 L' Original, only 16 miles distant. Here is found a section less than 

 200 feet in thickness, with sandstone at the base and limestone in the 

 upper portion. The fauna changes very abruptly, as several species of 

 ostracods that are unknown farther east, are found here. The other fos- 

 sils are : Camaroicechia plena, Raphistonia staniineuin, and Alalocxstites 

 viiirchisoni. From this locality west to Allumette Island, a distance of 

 115 miles, the same succession of strata may be found and about the 

 same fauna, but with some differences. At L'Original the ostracod 

 layers are below a fifty-foot bed of sandstone. In the sections farther 

 west, the ostracods occur in the limestone layers overlying the sand- 

 stone. Again, it is noticeable that the farther west from Grenville 

 the locality is, the fewer typical Chazy species are found. All through 

 the Ottawa Valley the Chazy is represented by a formation which is 

 sandstone at the base and limestone in its upper portion. 



The basal beds of the Chazy are always sandstone, but this sand- 

 stone does not carry the same fauna in all regions, nor do the strata 

 which rest upon it always carry the same fauna. In the region of 

 Lake Champlain, the sandstone always carries Lingiila brainerdi. In 



