THE GUMS OF TPIE PORPOISE PHOCGCXOIDES DALLI 



(TRUE) 



B}^ Gerrit S. Miller, Jr. 



Curalor, Division of M<unui(ils. I'nitcd li^tutcn Xatioual MuHeum 



The remarkabh^ small size of the teeth in the porpoises of the 

 aeiuis Phoccenoides is well known. (PI. 1.) True^ pointed it out in 

 liis original description of FJioeama dalll, the first species to be dis- 

 covered, and Andrews ^ later made it one of the diagnostic characters 

 upon Avhich he established Phoccenoides as a genus distinct from 

 Phocania. Specimens collected in Alaska by Ernest P. Walker have 

 brought to light the unexpected fact that the gums of P. dalli are so 

 modified as to form a set of secondary gum teeth, alternating with 

 and surrounding the true teeth, the extremities of which have come 

 to lie at the bottoms of pits between the bases of the new structures, 

 whose size and hardness is such that they are undoubtedly capable 

 of functioning as efficient grasping organs. (Pis. 2-4.) No such 

 condition has, to my knowledge, been described in anj'^ cetacean ; and 

 there is no known member of the order other than the two species 

 of Phocomoides (the Alaskan P. dalli and the Japanese P. truei) in 

 which the character of the dentition is such as to suggest that it 

 might exist. Whether or not the structures which I am about to 

 describe occur in Phocmnoides truei as well as in the Alaskan species 

 is a question which can not now be answered. Andrews says of the 

 type (p. 41) : " The teeth of this specimen are exceedingly small and 

 in life project but slightly above the surrounding membrane." This 

 remark seems hardly applicable to pit-ensconced teeth like those of 

 P. dalli; but the gums of the animal may have been injured in 

 skinning out the skull. 



The skulls with gums in place obtained by Mr. Walker are Nos, 

 243599 and 251757, I^.S.X.:\I., taken, respectively, at Wrangell on 

 September 7. 1922, and at Sullivan Island, Lynn Canal, in Xovem- 

 ber, 1926. There is also a nearly full term fetus (No. 251759) from 



> rroe. U. S. Nat. Mus., vol. 8, p. OG, May 20. ISS.^. 



2 Bull. Amer. Mus. Nat. Hist., vol. .30, p. .31, May 10, Iflll. 



No. 2771.— Proceedings U. S. National Museum, Vol. 74. Art. 26. 



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