330 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 52 



family. In spite of differences observable in living species, it seems 

 to me probable that the Delphinidas and Iniidas were derived from 

 common ancestors. 



In accounts of Stenodelphis which I have examined, the teeth are 

 described as having simple conical crowns. Professor Abel remarks 

 regarding the dentition of the genus that it presents "pas de trace 

 d'heterodontie."^ In two youngish skulls which I have examined, 

 however, ten or twelve pairs of teeth at the posterior end of the 

 series, in both the upper and the lower jaws, have incurved and 

 somewhat spatulate crowns, with rugose enamel, which is raised 

 into more or less linear denticles on the internal surface. Each tooth 

 usually presents a median denticle and indications of another on 

 either side of it, the general form being not unlike that occurring in 

 Delpliinapterns. I do not regard this character as differentiating 

 the rather composite genus Stenodelphis from the Delphinid?e, but 

 as strengthening the evidence that the Delphinidse were derived from 

 forms having tuberculate teeth. 



*Mem. Mus. Roy. Hist. Nat. Belgique, vol. 3, 1905, p. 42. 



