182 



GEOLOGY OF THE THIRD DISTRICT. 

 49. 



No. 1. Chemung goniatiie (G. chemungensis ), imperfect. 



2. Globulifonn atrypa (A. globuliformis), a cast. 



3. Chemung avicula (A. chemungensis J, two riews. 



No. 4. Chemung atiypa (A. chemungensis), two views. 



5. An imperfect convolute shell, which may be a Clymenia. 



6. Tricireled encrinite (E. triciclas). 



The Chemung group being so well characterized by its fossils, is the reason why so many 

 are given in illustration of it. Some of those of wood-cut 49 are very common or numerous ; 

 others are rare, but believed to be confined to the group. 



No. 1. The Chemung goniatite is rare; but being a large sized fossil, and only seen in this group, though 



it may not be a guide for the group elsewhere, it is a fact in its history. 

 No. 2. Globuliform atrypa. This cast is g^ven, because it exists in myriads as such in this group, 



numerous localities abounding in it. It is well represented in the engraving. 

 No. 3. Chemung avicula. This appears to be rather a common avicula, and is readily known by its 



well defined outline and its simple concentric markings. 



