27 



immediately above the Encriiial limestone occur vast num- 

 bers of the small Ambocoelia umbonata (Conrad), with the 

 sinus or depression in the centre ol the convex valve. ( Fig- 

 125, Ft. II. ). This fossil in some places almost makes u]) the 

 rock, and for a few inches in thickness scarcely an\' other 

 fossils occur. Occasionally crushed specimens of Athyris 

 spiriferoides (Eaton) occur with it, this fossil when first ex- 

 posed having a white or calcined appearance. A little higher 

 up, the large flat Stropheodonta perplaua ( Conr. ) occurs in 

 considerable numbers, and with it a small ]3atella-like 

 brachiopod — the PboUdops haniiltoni^e (Hall). The small 

 conical coral Streptelasma rectum (Hall) is also found. 

 Other corals occur, making u]) the "coral layer," which is so 

 well exposed in Section 5, under which it will be described. 

 The shale from two to three feet above the Encrinal lime- 

 stone is rich in two small species of Chonetes, which are 

 verj^ similar to each other, and both of which are char- 

 acterized by the possession of laterally projecting spines. 

 These are C. deflecta (Hall) and C. miicronata (Hall). The 

 type species, Spirifer consohrinus (D'Orb. ) is likewise abund- 

 ant in this portion of the rock. Above this Amhocoelia 

 umbonata (Conr.) gradually disappears, while the coarser 

 brachiopod Atrypa reticularis (Linn.) and the corals 

 Streptelasma rectum ( Hall ) and several species of Cvsti- 

 phyllum become quite abundant. A few crinoids also occur. 

 The trilobite Phacops rana (Green) occurs throughout the 

 five feet of shale containing this fauna, and it is the last to 

 disappear. Finally, it too, is no longer represented, and the 

 shale is barren to the base of the Spirifer tullius fauna, 

 except for the thin band with Orhiculoidea media ( Hall ) 

 already noticed. 



Section 5 (D). 



Plates VIII and IX. 



This is by far the longest and most interesting section in 

 the gorge. It lies on the right side of the stream, and begins 



