. Bulletin of the Geological Society of America. Geology. 152 SHIMER AND GRABAU—HAMILTON GROUP OF THEDFORD 111. Cyrtina hamiltonensis Hall. 112. C. hamiltonensis var. recta Hall. 119. Athyris cf. spiriferoides (Eaton). A. fultonensis (Swallow). Meristella rostrata Hall. 163. Hederella canadensis (Nicholson). 165. H. filiformis Nicholson. 170. Spirorbis .arkonensis Nich. 171. Spirorbis omphalodes Nicholson. 204. Aulopora serpens Rominger. 206. Ceratopora intermedia (Nicholson). 209. Trachypora elegantula Billings. 118 122 143. Reteporina prisca Nich. 155. Mstulipora utriculus Rom. 6. Blue clay,
. Bulletin of the Geological Society of America. Geology. 152 SHIMER AND GRABAU—HAMILTON GROUP OF THEDFORD 111. Cyrtina hamiltonensis Hall. 112. C. hamiltonensis var. recta Hall. 119. Athyris cf. spiriferoides (Eaton). A. fultonensis (Swallow). Meristella rostrata Hall. 163. Hederella canadensis (Nicholson). 165. H. filiformis Nicholson. 170. Spirorbis .arkonensis Nich. 171. Spirorbis omphalodes Nicholson. 204. Aulopora serpens Rominger. 206. Ceratopora intermedia (Nicholson). 209. Trachypora elegantula Billings. 118 122 143. Reteporina prisca Nich. 155. Mstulipora utriculus Rom. 6. Blue clay, poorly exposed and poor in fossils exposed 10 feet This section is entirely above the Encrinal limestone, and therefore belongs to the Upper Hamilton of this region. It is described by Logan on page 385 of his report. He says that the whole section abounds in fossils, but this does not hold for the lower beds, though their slopes are covered with weathered-out fossils from the beds above. SECTION B This section exposes the Encrinal limestone, which is about 2 feet thick and is divided into three beds. It was formerly quarried at this point. Just above the limestone is the coral layer, a decomposed shale full of corals, which are weathered out and may be picked up in large numbers on the surface. The most abundant and characteristic corals are: Heliop hyllum halli E. and H., H. tenuiseptatum x Bil- lings, Craspedophyl- l u m subcasspitosum (Nicholson), Cysti- phyllum vesiculosum (Goldfuss), Favosites billingsi Rominger, and F. placenta Rominger. Calvin (1888) cites Microcyclus discus Meek and Worthen as occurring in this division of the series, but this is prob- ably a mistake. No specimens were found in this exposure, the most typical of the coral layer, but the species is not uncommon at the base of the section at Bartlett's mills, and undoubtedly belongs to the lower Figure 2.—Section B—North of Thedford. Figures as in text. For scale see figure Pl
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