154 SHIMER AND GRABAU HAMILTON GROUP OF THEDFORD 



The coral bed is rich in Spirifer mucronatus var. thedfordensis. This 

 and the corals cover the slopes of the bank. The following list com- 

 prises the species picked up in a brief time, and is, of course, not an 

 exhaustive one : 



28. Platyceras subspinosum Hall. 139. Fenestella cf. arkonensis Whiteaves. 



57. Crania cranistriata Hall. 143. Reteporina prisca Nicholson. 



59. Pholidops hamiltonix Hall. 155. Flstulipora utriculus Rominger. 



64. Pholidostrophia iowaensis (Owen). ' 209. Trachypora elegantula Bill. 



71. Chonetes lepida Hall. 212. Cladopora frondosa (Bill.). 



79. Rhipidomella penelope Hall. 213. CI. roemeri (Billings). 



84. Camarotoschia thedfordensis Whiteaves. 214. Striatopora linneana Bill. 



86. Trig eria lepida Hall. 215. Alveolites goldfussi Bill. 



97. A trypa reticularis (Linn.). 217. Favosites digitata Rom. 



105. Spirifer mucronatus var. thedfordensis 218. F. placenta Rom. 



S. and G. 219. F. clausa Rom. 



111. Cyrtina hamiltonensis Hall. 230. Heliophyllum halli E. and H. 



114. Nucleospira concinna Hall. 231. H. tenuiseptatum Bill. 



115. Cryptonella sp. 233. Craspedophyllum subcsespitosum 



116. Rhynchospira eugenia(B\\\.). (Nich.). 



136. Semicoscinium labiatum Hall. 237. Cy stiphyllum vesiculosum Goldl uss. 



The limestone consists of crinoidal fragments mingled with fragments 

 of brachiopoda. Spirifer sculptilis was found in it. 



The black shale which separates the lower 8 inches of limestone from 

 the upper beds is filled with crushed valves of Leiorhynchus laura Bill. 



The lowest beds comprise a blue homogeneous clay or weathered shale, 

 with the stratification well marked, and almost destitute of fossils. It is 

 supposed to be at least 30 feet thick, and is sufficiently uniform and 

 free from lime to make good red bricks and tiles. 



SECTION D—ROCK GLEN 



In Rock glen the following section was measured in descending order : 



Drift. 



9. Bluish argillaceous limestone, often bituminous, containing many 

 Bryozoa and fragments of trilobites, in beds from 1 to 2 feet thick and 

 separated by beds of blue calcareous shale. Some of the beds are 

 filled with fragments of Ceratopora intermedia (Nicholson) 9 feet 



"8. Gray calcareous shales, with numerous small lime concretions disposed 

 in tiers. The lowest two feet abound in the characteristic Thedford 

 Spirifer 8 feet 



7. Blue argillaceous limestone containing a few Spirifer mucronatus var. 



thedfordensis, but scarcely any other fossils 1J feet 



6. Blue calcareous shale, including, four feet from the top, a foot or more 

 of harder calcareous beds. Fossils are rare, excepting a few speci- 

 mens of the characteristic Thedford Spirifer 18 feet 



