420 The Uppi-r Devoxiax Deposits of Maryland 



whicli are jasper. A similar massive sandstone, containing the Tropido- 

 leptus carinatus fauna, occurs abo\it 300 feet above the base of the Che- 

 mung west of Wills Mountain. While it may represent the same horizon, 

 it is not possible to affirm this confidently, because of the differences in the 

 sections east and west of Wills Mountain. 



Among the most important species occurring in these beds are Tropi- 

 doleptiis carinatus, Spirifer mnrcyi vai'. supersics, Rhipidomella vanuxemi 

 and other species of Hamilton affinities, a complete list' of which is 

 given in the table of distribution. The recurrence of a fauna of pro- 

 nounced Hamilton affinities above the base of the Chemung is of much 

 interest. 



Middle Shale and Sandstone Beds. — The preceding division is over- 

 lain by shales and interbedded sandstones. West of Wills Mountain a 

 very massive gray and brown conglomeratic sandstone occurs between 

 the upper and lower conglomerates. It is not improbable that it is in 

 the middle of this division, though its relation is not assured. A list of 

 the species observed in this division is given in the table of distribution. 

 No distinctive features have been recognized in this fauna. 



Upper Conglomeratic Sandstone Beds. — A zone of massive conglomer- 

 atic sandstones occurs in the sections east of Wills Mountain, about 800 

 feet above the lower conglomerate. No distinctive fauna has been ob- 

 served in it, but the constancy with which the conglomerates appear at 

 about the same horizon, and the fact that they are always very massive 

 and ridge-forming, leads to the conclusion that they probably constitute 

 one horizon. West of Wills Mountain a similar, very massive, ridge- 

 forming conglomerate occurs 500 to 800 feet below the top of .the Jen- 

 nings and probably represents the same horizon. 



The upper conglomerate contains flat quartz pebbles, which are often 

 large. Some jasper pebbles are also found in it. The cement is so firm 

 that the rock usually breaks across the pebbles the fractured faces of 

 M'hich present a polished appearance. An attempt has been made to dis- 



' In the Woodmont section the Tropidoleptus fauna occurs 54 feet above 

 what appears to be the lower conglomerate. Whether the fauna is higher 

 than usual or the conglomerate is at a lower horizon in that section is not 

 known. 



