TROPIDOLEPTUS FAUNA IN MARYLAND CHEMUNG 683 



road, a lower massive conglomerate is exposed, holding essentially the same 

 position as the Tropidoleptus-bearing zone west of Okonoko. It bears Tropi- 

 doleptus carinatus. This species, and others found in the preceding sections, 

 were observed at numerous points in the vicinity on the strike, lying about 

 500 to 700 feet above the base of the Spirifer disjunct us fauna. The latter is 

 constantly underlain by the lower Tropidoleptus fauna, below which appears 

 the Ithaca fauna. It is thus possible to trace a continuous horizon, which is 

 very conglomeratic in the east, much less so in the west, and which bears 

 Tropidoleptus carinatus lying at an altitude of about 2,500 to 2,700 feet above 

 the base of the Jennings. 



MORE EASTERLY SECTIONS 



A persistent and massive conglomerate appears at approximately the same 

 altitude in the sections farther east. They have not yet been studied with 

 respect to the occurrence of Tropidoleptus carinatus, but it is believed that 

 they represent the same horizon. 7 



Sections West of Wills Mountain 



section near allegany grove 



When we pass west of Wills mountain the sections show marked faunal and 

 lithological changes, though they are but a few miles distant from the most 

 westerly sections previously described. 



The best section of the region is near Allegany Grove, about four miles south- 

 west of Cumberland, along the Cumberland and Potomac, and the Georges 

 Creek and Pennsylvania railroads. The lower part of the section consists 

 largely of argillaceous shales. At an altitude of about 800 feet above the base 

 of the Jennings, CamarotcecMa sp. was found in somewbat more arenaceous 

 sediments. At an altitude of 1,360 feet Spirifer disjunctus occurs. At 1,560 

 feet massive sandstones develop. The Tropidoleptus carinatus fauna is found 

 in these strata a short distance south of the railroad. At 1,900 feet a heavy 

 conglomerate appears associated with gray and brown sandstones. At 2,600 

 feet is a second massive conglomerate, which is revealed only by fragments in 

 the section on the railroad. Several other less prominent conglomerates are 

 seen above this. The Catskill appears at the east end of the tunnel at an alti- 

 tude of 3,000 feet above the base of the section. 



SECTION NEAR ELLERSLY 



At Ellersly, 6y 2 miles northeast of the preceding section on the strike, a pro- 

 fuse development of Dalmanella tioga (Hall), Spirifer disjunctus, and other 

 characteristic Chemung forms appears at an elevation of about 1,300 feet. 

 The same zone may be traced southwestward nearly to the Potomac river, 

 showing that the Spirifer disjunctus fauna appears at about 1,300 or 1,400 feet 

 above the base of the section. Tropidoleptus carinatus was observed abun- 

 dantly at a number of points southwestward on the strike in what appears to 

 be the massive sandstone occurring at 1,560 feet altitude in the Allegany 



7 Since the above was written the Tropidoleptus carinatus fauna has been found at the 

 appropriate horizon in the section near Mann, east of Sideling Hill. 



