g6 NEW YORK STATE MUSEUM 



crushed valves of small plicated brachiopods, among which A n o - 

 p 1 o t h e c a h e m i s p h e r i c a and A. p 1 i c a t u 1 a may be 

 mentioned. Other fossils are rarely found except reed-like impres- 

 sions which are not uncommon. Some impressions have been found 

 which probably belong to Pterin aea emacerata, a pelecy- 

 pod occurring higher in the Clinton and also in the Rochester 

 shales. The total thickness of these shales is 6 feet. 



Clinton lower limestone. On the shale rests a stratum of lime- 

 stone 14^ or 15 feet in thickness. The lower three or four feet of 

 this rock are compact to granular or finely crystalline, having a 

 sugary texture. Small masses of iron pyrites are not uncommon 

 in this rock^ this being the only representative of the ferruginous 

 matter so characteristic of this part of the Clinton beds on the 

 Genesee river and eastward, where a well marked bed of iron ore 

 succeeds the shale. Hall^ states that " the lower part of the lime- 

 stone, as it appears on the Niagara river, is highly magnesian, and 

 from the presence of iron pyrites rapidly decomposes, giving rise to 

 the production of sulfate of magnesia, which at favorable points 

 along the overhanging mass upon the river bank, may be collected 

 in quantities of several pounds." 



Fossils are not uncommon in this division of the Clinton lime- 

 stone, though the variety is not very great. The most abundant 

 species are a small brachiopod, Anoplotheca plicatula 

 (fig. 133) with a strongly plicated surface, and a larger flat 

 brachiopod, S t r o p h e o d o n t a profunda, which at times 

 seems scarcely more than an impression on the rock surface. The 

 remaining part of this stratum is a massive dark gray limestone 

 with occasional thin bands of a shaly character separating the in- 

 dividual beds. Recognizable fossils are not very abundant in this 

 rock. Many of the thin bedded portions of the lower Clinton lime- 

 stone contain numerous shining black phosphatic nodules, very 

 smooth and resembling small black pebbles. These are probably 

 concretionary masses, though some have the aspect of being water- 

 worn organic remains. Where the thin limestone layers are covered 

 with a shaly or sandy coating, impressions of the beautiful, little 



^Rep't 4th dist. 1842, p. 63. 



