IN THE RED SANDSTONE OF I'OTTSVILLE. 13 



pubsjlobular forms, which may possibly be the cjcetamenta or coproHtcs of some of the 

 animals that passed over the shores of these waters. 



Another of the specimens which I obtained at the same time, contains the remains of 

 a portion of an organic form, which I cannot with any satisfaction make out. It is pro- 

 bably a very small portion of the whole organism, as it forms only a short, curved, ser- 

 rated line of an inch and half in length. (Fig. 1.) I cannot compare this serrated line to 

 any like form, but that of the serrated edge on the side of the Olenus asaphoides, of Hall's 

 Palaeontology, (part 4, pi. 67, fig. 2,) and Asaphus Buchii, in the Llandeilo Flags, (Silurian 

 Syst., pi. 25, fig. 2,) in which the serrations are, however, more pointed. Mr. Hall's speci- 

 men is from the Hudson River Group, Formation No. 3, of the Pennsylvania Report, a 

 period far removed and earlier than Formation 11, in which this specimen was found, 

 near to Pottsville. The serrated edge of ElUpsocephalus Hoffii, Zenker, in Burmeister's 

 "Organization of Trilobiles," (p. 74, pi. 1, fig- 8,) approximates very closely, in outline, to 

 our figure. 



In 1834, Mr. Taylor communicated to the Geological society of Pennsylvania that he 

 had observed "at least two nondescript species of Fucoides in the Old Red Sa7idstone of 

 Tioga county, Pennsylvania." (Transactions, vol. 1, p. 175.) And he subsequently ob- 

 served obscure impressions of plants in the same formation, near to Pottsville, at Tum- 

 bling Run Dam. This obscure vegetation has been observed also by others, and there 

 are now specimens in the collection of the Academy of Natural Sciences of this city. 



The red sandstone rocks of this period present frequent and marked instances of cracks 

 caused by dessication of the mud which opens into irregular fissures, which, on return of 

 the tide, were probably filled up by sand, thus sometimes furnishing a tissue of meshes of 

 various sizes, the interspaces being sometimes as great as three feet. A very remarka- 

 ble one of this kind may be seen at Dauphin, near the Susquehanna, above Harrisburg, 

 in this red sandstone, underlying the coal measures of that part of the same basin. The 

 surface of the rock exposed there with these sun-dried sand-cracks, must be quite thirty 

 feet, and some of the cracks were nearly a foot across. 



