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GEOLOGY OF THE THIRD DISTRICT. 
49. 
No. 1. Chemung goniatite (G. chemungensis ), imperfect. No. 4. Chemung atrypa (A. ehemungensis), two views. 
2. Globuliform atrypa (A. globuliformis), a cast. 5. An imperfect convolute shell, which may be a Clymenia. 
3. Chemung avicula (A. chemungensis), two views. 6. Tricircled 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 given, 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. 
