32 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 72 



probably used, in a similar manner to the upper canine in the walrus 

 or to the tip of the snout itself in the Eurhinodelphines, for rooting 

 in the sea bottom. Such a function might be initiated by forward- 

 slanting anterior teeth like those in Delphinaptenis, but later it must 

 have been restricted to the ramming-tooth in the left jaw of males. 

 The work of the males may possibly be of service to the females 

 because the species is gregarious. The ramming-tooth has become a 

 kind of male secondary sexual character and has grown to an ex- 

 aggerated size as the well-known " unicorn horn." As a memento of 

 an earlier condition the ramming-tooth is still found in a reduced 

 form in the right upper jaw of the male, and in both upper jaws of 

 the female ; in rare instances it may even now be found in the male 

 well developed on both sides [when the spiral of the two tusks is 

 parallel]. 



All the other Delphinids are contrasted with the Eurhinodelphines 

 and Monodonts by the partial or complete coalescence of the cervical 

 vertebrae, the atlas and axis being always united. The genera in 

 question constitute a compact group, rich in forms, which traces its 

 origin back to low Eurhinodelphines. 



Lowest of all stands the section Delphini, whose most primitive 

 known genus is imdoubtedly Steno. This has still the primitive 

 Eurhinodelphines' long, but not exaggeratedly long, narrow, scarcely 

 flattened fore-face, with long toothrows and long symphysis menti. 

 It is indeed scarcely distinguishable from the primitive Eurhinodel- 

 phines except by its partly ankylosed cervical vertebrae. The circum- 

 stances which place it low among its nearest relatives are the facts 

 that the teeth have fluted enamel, and that the symphysis menti is 

 long. The peculiarity of the enamel is presumably a slight reminis- 

 cence of an earlier, less-reduced condition. 



Very near Steno comes Prodelphinus (probably including " Sota- 

 I'm"), not differing in much else than that the enamel is smooth, not 

 fluted, and that the symphysis menti is shortened. 



Delphinus differs from Prodelphinus in scarcely anything else than 

 a peculiar palate form: at the inner side of the toothrow the bony 

 palate is hollowed out into a long longitudinal furrow which is 

 especially deep behind. The intermaxillaries have a relatively strong 

 tendency to coalesce and to cover over the mesethmoid. A few small 

 teeth may be found in the intermaxillary as in Steno and Prodel- 

 phinus; in most of the Delphinids the teeth have wholly disappeared 

 therefrom. 



In contrast to the Delphinines the other higher Delphinids have 

 the skull's fore-face shorter and more depressed. As a beginning the 



