1938.] NATURAL SCIENCES OF PHILADELPHIA. 29 



in 1890.^*" This tooth and one other are blackish in color, while 

 the third tooth is yellowish. The last mentioned is 21 mm. long, and 

 that figured by Cope 23 mm. 



As mentioned by Cope, both crown and root are compressed, the 

 former at right angles to the latter." This form of tooth occurs in 

 Stenodelphis and in some genera of DelphinidcB. The crown is slightly 

 recurved. The base of the crown is somewhat convex, both internally 

 and externally, and is marked off from the root by a distinct con- 

 striction, due in part, no doubt, to wear. 



Teeth similar to these in size and form, from Baltringen, Wiirtem- 

 berg, Germany, were described and figured by Dr. J. Probst in 1886,^^ 

 under the name of Schizodelphis canaliculatus H. von Meyer. This 

 species is considered identical with S. sulcatus by Dr. Abel, but the 

 teeth of the latter, figured by Dal Piaz,*^ are certainly different, as 

 regards the shape of the crown and the direction of its compression, 

 from those figured by Probst. Even with allowance for variation, 

 it seems to me probable that they may represent two different species 

 of the genus Schizodelphis. The principal difference between the 

 teeth assigned to Rhabdosteus and those figured by Probst is that the 

 crown is shorter in the former. 



On the whole, it seems probable that the teeth described by Cope 

 belong to the genus Schizodelphis, but this is not a sufficient reason 

 for considering Rhabdosteus synonymous with Schizodelphis, especially 

 in view of the fact that it is uncertain whether the teeth have any 

 direct connection with the type rostrum of Rhabdosteus. The most that 

 can be said is that the alveoli of Rhabdosteus indicate that the teeth 

 had flattened roots of the same size as those of the teeth which Cope 

 assigned to that genus. 



Explanation of Plate VI. 



Plate VI. — Fig. 1. — Type specimen of Rhabdosteus latiradix Cope. Superior 

 surface. Scale p;. 

 Fig. 2. — The same. Left side. Scale ^. 

 Fig. 3. — The same. Inferior surface. Scale ^j. 



1" Amer. Nat., 1890, p. 607, fig. 4 (2, 2a, 2b). 



" That the anterior and posterior surfaces of the crown are flat is not due to 

 wear. 



" Jahreshefte Ver. Vaterldnd. Naturkunde W urttemberg , 42, 1SS6, PL 3, figs. 

 11-14. 



" Palceont. Ital., 9, PI. 31, figs. 6-2S. 



