196 The Ottawa Naturalist. [Feb. 



land is so full of Camarotaechia plena. There is nothing 

 in the typical Chazy which corresponds to the ostracod 

 layers such as the clavigera zone and the limestone in the 

 20 feet above it. Excepting the ostracods, nearly all the fossils 

 from this horizon upward are species found also in the Black 

 River and Trenton. The fauna found in the upper 15 feet is 

 evidentlv Lowville, Tetradium cellulosum and Bathyiirus extans 

 being the guide fossils. Many of the fossils found below this 

 laver are known in the Lowville but the absence or rarity of 

 Tetradium cellulosum gives the fauna a slightly different aspect. 

 It niav be significant that this Tetradium first becomes common 

 in beds above the "pebble beds" (No. 1. in the section at Mech- 

 anicsville.) The pebbles in these beds are from 1 to 3 inches in 

 diameter and have well rounded edges. They are somewhat 

 greenish in color, and remind one of some of the green limestone 

 layers in the upper part of the Chazy at the Hogs Back. They 

 are in a rather ptire limestone matrix which is very fossiliferous, 

 Cyrtodonta huronensis being abundant, and cephalopods common. 

 Though it cannot be called a conglomerate, this bed indicates 

 some sort of a physical change, and, coupled with the slight 

 change in fauna, may prove to be of some importance. 



While the pebble bed may be the base of the Lowville, it 

 seems more probable that the line should be drawn 35 feet lower 

 down, at the base of the sandstone containing Clionychia and 

 Vanuxemia (No. 6 of the second section at the Hogs Back and 

 No. 4 of the section on the road beyond Robillard's quarries.) 



At the Hogs Back there are two of these thick beds of sand- 

 stone, which, coming as they do in the midst of a series of lime- 

 stones, indicate a pronounced change in the conditions govern- 

 ing sedimentation. The change in the fauna at this point, 

 though not striking, can be seen. The principal difference noted 

 is in the ostracods, which, below this sandstone are often so 

 abundant as to make up the entire mass of certain layers, and, 

 moreover, these ostracods are usually smaller than those found 

 above. Certain species, such as Tsochilinaf clavigera and Bathy- 

 urus angelini, are not found above this sandstone. 



These rocks which lie above the highest bed containing 

 Camarotaxhia plena and below the sandstone with Vanuxemia 

 and Clionychia are similar, lithologically, to a formation which 

 occtirs in northwestern New York. This formation was described 

 by Dr. H. P. Gushing.* who gave it the name Pamelia. The 

 formation, in New York, is from 60 to 150 feet thick, and con- 

 sists of 10 to 20 feet of shale and sandstone at the base, 



*Bull. Geol. Soc. Am. Vol. 19, p. 55, 1908 



