Geology.- 



123 



that formation, near Phoenixville, on the Schuylkill, the tooth of a Sau- 

 froid Reptile, which he thus characterized. 



Centemodon* sulcatus. — Tooth smooth, rather thick, slightly curved, 

 with trenchant edges, rounded on the exterior portion, sulcate on the 

 lower part near the base, covered with very minute distinct striae from 

 the point to the base, which striae cross the sulcations in slightly oblique 

 lines. Length sixteen-twentieths of an inch, greatest breadth four-twen- 

 tieths of an inch ; pulp cavity large. 



On comparing this tooth with Ctepsysaurus Pennsylvanicus, which he 

 had described from the same Red Sandstone formation in Lehigh county, 

 it will be found to differ very widely. The edge is not serrate on any 

 part like that genus, nor is it so large or so attenuate. The form, too, is 

 more compressed. It differs from the teeth of Bathygnathus boreali?, 

 Leidy, from the New Red Sandstone of Nova Scotia, in size, being 

 smaller and more attenuate, as well as in having a trenchant smooth 

 edge and not a serrate edge. It is about the size and approaches the 

 form of Prof. Owen's figure of Labyrintkodon, plate 63, A. f. 2, of Odon- 

 tographia, but it is more flattened. 



Mr. Lea also stated that in the greenish and blackish shales of the 

 same locality he found two species of Posidonia, which genus is so char- 

 acteristic of this portion of the formation and existing in immense quan- 

 tities. As they seem to differ from that figured by Sir Charles Lyell, in 

 his Elementary Geology, as coming from Oolitic coal shale of Richmond, 

 Virginia, Mr. Lea proposed the names of P. ovata and P. parva, the first 

 being about seven-twentieths of an inch in transverse diameter. The 

 latter is more rotund, and about three-twentieths of an inch in transverse 

 diameter, both being covered with numerous minute concentric costse 

 over the whole disc. 



Near to this locality and superimposed, Mr. Lea obtained a specimen of 

 impure dull red limestone, which contained, on a partially decomposed 

 surface, impressions presenting the appearance of -Foot-marks, somewhat 

 like Ckelichnus Duncani, Owen, figured by Sir Wm. Jardine in his Ich- 

 nology, for which Mr. Lea proposed the provisional name of Ckelichnus 

 Wymanianus, after Professor Wyman, of Cambridge, Mass. 



From the same formation and locality were procured the impressions 

 of plants, some of which belong to the^UonifercB. One of the cones was 

 nearly six inches long and full an inch wide. These were accompanied 

 by other plants of very obscure character, covering large portions of the 

 surface of some of the layers. 



Mr. Lea also mentioned that he had observed the same red, black and 

 gray shales at Gwinnedd, on the North Pennsylvania Railroad, where he 

 found the same Posidonice, and some of the same obscure plants, impres- 

 sions of which covered the surfaces of many of the rocks. A single 

 specimen was obtained of a plant with long leaves somewhat resembling 

 v Noeggerraihia cuneifolia, Brongniart, which is from the Permian. 



In the black Posidonia shales was found a single Ganoid scale, which 

 is more like Pygopteris mandibularis, Agas., from the -Marl Slate (Lower 

 Permian) than any other which had come under Mr. Lea's notice. There 

 were other obscure forms observed, which have not been satisfactorily 



* KtvTxjua, aculeus, and odovt, dens. 



