MesozoiG and Cmnozoic Geology and Palceontology. 213 



of the greatest abundance of Leda truncata^ the most exclusively 

 Arctic shell of these deposits. In other words, he regarded the plants 

 above mentioned as probably belonging to the period of greatest re- 

 frigeration of which we have any evidence — of course, not including 

 that mythical period of universal incasement in ice, of which, in so 

 far as Canada is concerned, there is no evidence whatever. 



The Tertiary formation * exists in the southern part of the State 

 of Illinois. It is best developed in Pulaski and Massac counties. 

 It is represented by a series of stratified sands and clays of various 

 colors, with beds of silicious gravel, often cemented into a ferrugin- 

 ous conglomerate by the infiltration of a h3'droxyd of iron. In some 

 places it contains green, marly sand, with casts of fossils, and along 

 the edge of the Ohio, at extreme low water, at Caledonia, there is a 

 thin bed of lignite. At Fort Massac, just above Metropolis, the fer- 

 ruginous conglomerate is from forty to fifty feet in thickness. Near 

 Caledonia, a section gave a thickness of 56|- feet. 



T. A. Conradf described, from the Miocene of the Eastern and 

 Southern States, Nassa suhcylindrica, Volutifusus typiis^ Cancellaria 

 scalarina, Saxicava parilis, S^nsula capillaria, Tellina peracuta, T. 

 capillifera, Astarte Gomp&onema^ Lithophaga suhalveata, Macoma 

 virginiana, Mercenaria obtusa, and Ciimingia medialis. 



Philip P. Carpenter;]; desci'ibed, from the Pliocene of Santa Barbara, 

 California, Turritella jewetti, Bittium armillatum, Opalia insculpta, 

 Trophon tenuis c^ilptus, and Pisania fortis. 



In 1867, Prof. E. W. Hilgard§ said that nowhere has the geologist 

 more need of divesting himself of reliance upon lithological characters, 

 than in the study of the Mississippi Eocene. Not only do the materials 

 of the diff"erent groups often bear a most extraordinary resemblance to 

 each other, but their character varies incessantlj^ in one and the same 

 stratum, within short distances. Hale remarks that in Mississippi, 

 the Orbitoides limestone seems to be represented by blue marlstone, 

 and so it is, sometimes. But while on the one hand we see the hard 

 limestone of the Vicksburg blufi" passing into blue marl (Bjn-am, 

 Marshall's quarr}-), we on the other hand find it passing equally into 

 a rock undistinguishable from that of St. Stephens (Brandon, Wayne 

 count}') ; the varied fossils described by Conrad disappearing almost 



* Geo. Sur. of 111., vol. i. 



t Am. Jour. Conch., vol. ii. 



i Ann. <fe Mag. Nat. Hist., 3d ser., vol. xvii. 



$ Am. Jour. Sci. & Arts, 2d ser., vol. xliil. 



