EXPLANATION OF PLATES. 



Plate 1. 



FiG.l. Mesoplodonbidens. SkuU. Nantucket, Mass. Mus. Comp. Zoology, No. 1727. Female, adult. 

 Dorsal aspect. About J nat. size. 

 Extremity of beak defective. 

 2. Mesoplodon densirostris? Skull. Annisquam Mass. Female, young. Boston Society of Natural 

 History. Dorsal aspect. \ nat. size. 

 Defective on the left side. 



Plate 2. 



Fig. 1. Mesoplodon europxus. Skull. Atlantic City, New Jersey. Male, young. Cat. No. 23346, 

 U.S.N.M. Dorsal aspect. \ nat. size. 



2. Mesoplodon europmus. Skull. North Long Branch, .New Jersey. Female, adult. Mus. 



Comp. Zoology. Dor.'ial aspect. | nat. size. 

 Distal portion of beak lacking and right frontal region defective. 



3. Mesoplodonbidens. Tooth. Nantucket, Mass. Mus. Comp. Zool.. No. 1727. Nat. size. 



Plate 3. 



Fig. 1. Mesoplodon stejnegeri. Type-skull. Bering Island. Immature. Cat. No. 21112 U.S.N.M. 

 Dorsal aspect. J nat. size. 

 Edges abraded; distal end of beak defective. 

 2. Mesoplodon stejnegeri. Skull. Yaquina Bay, Oregon. Adult. Cat. No. 143132, U.S.N.M. 

 Dorsal aspect. } nat. size. 

 Proximal end of premaxillae defective and right nasal lacking. 



Plate 4. 



Fig. 1. Mesoplodon bidens. Skull. Nantucket, Mass. Female, adult. Mus. Comp. Zool. No. 1727. 

 Ventral aspect. About i nat. size. Tip of beak, left pterygoid, and malars defective. 

 2. Mesoplodon densirostris? Skull. Annisquam, Mass. Female, young. Boston Society of Nat- 

 ural History, Ventral aspect. { nat. size. 

 Left frontal region defective 



Plate 5. 



Fig. 1. Mesoplodon europxiis. Skull. Atlantic City, New Jersey. Male, young. Cat. No. 23346, 

 U.S.N.M. Ventral aspect. \ nat. size. 

 2. Mesoplodon europsms. Skull. North Long Branch, New Jersey. Female, adult. Mus. Comp. 

 Zoology. Ventral aspect. \ nat. size. 

 Distal portion of beak lacking, pterygoids, malars, and left frontal and temporal regions defective. 



Plate 6. 



Fig. 1. Mesoplodon stejnegeri. Type-skull. Immature. Cat. No. 21112, U.S.N.M. Ventral aspect. 

 \ nat. size. 

 Edges abraded; tip of beak, pterygoids, zygomatic processes, etc.. detective. 

 2. Mesoplodon stejnegeri. Skull. Adult. Cat. No. 143132, U.S.N.M. Ventral aspect. About 

 \ nat. size. 

 Pterygoids and left malar defective. 



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