Am. Jour. Sci., Vol. XVII, 1904. 



Plate XV, 























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1. — Orthothetes chemungensis var. pectinacea Hall, x 2. 

 2. — Orthothetes chemungensis var. arctistriatus Hall, x 2. 

 3. — Orthothetes bellulus Clarke, x 2. 

 4, 5. — Chonetes mucronatus Hall, x 2. 

 6. — Cyrtina hamiltonensis Hall. x2. 



