1915.] NATURAL SCIENCES OF PHILADELPHIA. 565 



limy character of the upper harder layers is pronounced. They 

 stand out as a prominent escarpment for about 1| miles between 

 Half Acre and Oakwood." East and a little south of Oakwood on 

 the boundary line between the to\\Tis of Fleming and Springport 

 another good exposure of Mottville is found. At the point where 

 the roadway on the map is marked with an altitude of 707 feet the 

 harder layers of the Mottville are finely displayed. As stated 

 above, these harder layers undergo a certain amount of progressive 

 change toward the west. They are now quite limy and of bluish 

 shades which become lighter on exposure. Prolonged weathering 

 produces a duller and more rusty appearance which, together with 

 numerous ''cauda-galli" markings, causes a curious resemblance 

 to the very much higher beds which are usually assigned to the 

 Ludlowville. At this town line exposure the relations with the 

 Agoniatites limestone are again determinable, for the latter is exposed 

 in a field south of the road which parallels the Lehigh Valley track. 



At the four corners which lie about 1^ miles south and a little 

 -east of Oakwood the Mottville is again displayed and is connected 

 by a fairly well-marked escarpment with the localities northeast. 

 Here at these four corners the relations with lower strata can be 

 made out, the Agoniatites limestone outcropping at the slight bend 

 in the north-leading road f mile to the north, the Onondaga lime- 

 stone and Styliolina layers by the roadside about f mile to the west. 

 The writer wishes to emphasize the fact that his interpretation of 

 the stratigraphy between Half Acre and these four corners is based 

 ■on evidence furnished (1) by lithologic and paleontologic similarity 

 of the different Mottville exposures, (2) by the position of each 

 exposure with reference to some easily recognized lower stratum 

 and (3) by the occurrence of the exposures on the edge of a hard 

 rock platform which frequently displays a well-marked escarpment 

 •on its northern and northwestern fronts. These lines of evidence 

 lead to a conception of the stratigraphy, Avhich is quite chfTerent 

 from that sho^^^l on the geologic map of the Auburn quadrangle.^^ 



On approaching Cayuga Lake the harder portion of the Mottville 

 produces the falls just east of the lake road in Great Gully Brook 

 ^nd in the next brook south which is unnamed on the map.^^ This 

 latter is apparently the Crise's Brook of Vanuxem and is called 



" See Vanuxem, Geology of the Third District, p. 154. 



12 N. Y. State Museum Bulletin 137. 



13 See Cleland, U. S. G. S. Bulletin 206, pp. 22, 23, and also Luther, N. Y. 

 +State Museum Bulletin 137, p. 19. 



