No. 2007. DESCRIPTION OF ME80PL0D0N MIRUM—TRUE. 657 



From hectori it differs in the greater breadth of the cranium, the 

 size and shape of the maxillary ridges and anteorbital notches, the 

 concavity of the superior margin of the temporal fossae, the much 

 shorter vertex, etc. It bears no close resemblance to stejnegeri. 



The shape of the mandible is similar to that of the last-named 

 species, but the symphysis is somewhat longer, and the position and 

 size and form of the teeth are entirely different. M. hectori is the 

 only known species besides mirum that has the teeth at the extremity 

 of the mandible, but the skull of the former, as already remarked, 

 presents quite different characters from that of mirum. 



EXPLANATION OF PLATES. 



Mesoplodon mirum True. Type-specimen, Cat. No. 175019, U.S.N.M., Beaufort 

 . Harbor, North Carolina. Adult female, 16 feet long. 



Plate 52. 



The type-specimen lying in Beaufort Harbor. Head dissevered and fins somewhat 



mutUated. 



Plate 53. 

 Fig. 1. Head, superior aspect. 



2. Head, lateral aspect. 



3. Head, inferior aspect. About xt natural size. 



Plate 64. 

 Skull, superior aspect. About one-fifth natural size. 



Plate 55. 

 Skull, inferior aspect. About one-fifth natural size. 



Plate 56. 

 Skull, lateral aspect. About one-fifth natural size. 



Plate 57. 



Fig. 1. Mandible, left side. About one-fourth natural size. 



2. Symphysis of mandible, showing the teeth in position. About seven- tenths 

 natural size. 

 80459°— ProcN.M. vol.45— 13 42 



