i82 Natural History Bulletin. 



■pora. On the west side of the river, about a quarter of a 

 mile below the dam at Littleton, jVczvberria johannis Hall, 

 was found in place. It is confined to a thin layer of yellow, 

 shaly limestones which lies immediately above layers contain- 

 ing Acervidaria -profunda Hall, and it may be convenient to 

 regard this yellow calcareous shale as the uppermost limit of 

 the sub-division which is here called the Acervularia profunda 

 beds. In the same thin layer with JVewberria johannis H., 

 there occur Tcrebratida romingeri H., and Pentamerella 

 arata H. 



Immediately above the calcareous shales containing New- 

 herria^ the fauna undergoes a very marked change. Sph'ifera 

 parryana H., takes the place of S. pennata Owen. Atrypa 

 aspera is absent. A. retictdaris has become more ventricose, 

 with cardino-lateral angles more rounded and the radiating 

 costae much coarser than in the A. retiadaris of the pennata 

 beds. Stropliodonta demissa Con., becomes very large, hav- 

 ing in mature specimens a width of two inches at the hinge- 

 line \vith a length of more than an inch, and presents an 

 appearance very different from the small, short hinged, arcu- 

 ate, coarsely ribbed forms, rarely more than three quarters 

 of an inch in width, found associated with Spirifera pennata^ 

 at Independence. The layers containing S. parryana are 

 followed by a compact reef of Acervidaria davidsoni Ed. 

 and H., with which are associated Favosites^ Ptychophyllum, 

 Cladopora and some other genera. The beds included be- 

 tween the calcareous shale containing JVezubcrria and the sum- 

 mit of the reef of Acervidaria davidsoni and associated corals, 

 constitute the Acervidaria davidsoni beds. 



On the west side of the river at Littleton, near the end of 

 the mill dam and for some distance below it, the rocks above 

 the reef of A. davidsoni are yellow colored, indurated shales 

 which grade up into softer shales that readily weather on 

 exposure into a yellow clay mixed with harder fragments that 

 resist the action of the weather. The harder layers in the 

 lower part of this division of the section contain no fossils as 



