Pi Aah eX ee 
RHYNCHODUS EXCAVATUS, Newb. (p. 50). 
Fic. 1. Left lower tooth, natural size. 
Hamilton group, Brown Deer, Wis. 
18. Section. 
RHYNCHODUS FRANGENS, Newb. (p. 48). 
2. Lower left dental plate, outside view, natural size. 
2, Triturating face of Fig. 2. 
Corniferous limestone, Delaware, Ohio. 
3. Solid triturating angle of right lower dental plate, inside view, natural size. 
Corniferous limestone, Kelley’s Island, Lake Erie. 
MACHE®RACANTHUS MAJOR, Newb. (p. 39). 
4. Short and robust pectoral spine, upper side, natural size. 
48, Section of same. : 
Corniferous limestone, Delaware, Ohio. 
MacH#®RACANTHUS SULCATUS, Newb. (p. 40). 
5. Pectoral spine, under side, natural size. 
58. Section of same. 
Corniferous limestone, Canada. 
MaCHZRACANTHUS PERACUTUS, Newb. (p. 38). 
6. Pectoral spine, upper surface. 
Section. - 
Corniferous limestone, Delaware, Ohio. 
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