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 portion. . 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 

 beds. 



Figure 2.— Section B — North of Thedford. 

 Figures as in text. For scale see figure 4. 



