jiBT. 19 A MIOCENE PORPOISE FROM MARYLAND KELLOGG 33 



formation of Maryland. With the possible exception of Platanista 

 croatica ^- and Heterodelphis leiodontus ^^ they do not resemble any 

 of the teeth described from European formations. 



These teeth differ from those of Delphinodon dividum " in so 

 many respects that there is hardly any possibility of confusing them. 

 To emphasize the differences existing between the teeth of these two 

 small dolphins their main characteristics may be summarized as 

 follows: In Delphinodon dividum the crowns of the teeth are re- 

 curved, with a carina on the anterior and posterior cutting edges, 

 and the enamel is rugose; the posterior teeth have one or more ac- 

 cessory cusps ; the roots are slender, elongated, somewhat gibbous be- 

 low the base of the crown, curved backward at the extremity, and 

 have a large dentinal canal. The largest teeth have a length of 29 

 mm. and a maximum diameter of 5 mm. ; the smallest teeth are 20 mm. 

 long and have a maximum diameter of 4 mm. ; the teeth are more 

 or less crowded in the upper and lower jaws. In comparison to 

 those of DelpMnodon dividum the majority of the teeth of this por- 

 poise are shorter, more slender, and have less swollen roots; the 

 crowns are recurved, but the enamel is relatively smooth; neither 

 accessory cusps nor carinae are present on any of the teeth ; one of 

 the largest teeth has a length of 38.3 mm. and a maximum diameter 

 of 3.9 mm. ; the smallest teeth are 13 mm. long and have a maximum 

 diameter of 2.8 mm. ; the teeth in the upper and lower jaws are sepa- 

 rated by intervals slightly less than the maximum diameter of the 

 oi)posing teeth. The anteriormost tooth on each side is greatly 

 elongated, inserted in the extremity of the premaxilla, and projects 

 forward and slightly downward. The crown of this large tooth 

 measures 11.5 mm. in length and 3.5 mm. in diameter at the base; 

 it tapers gradually and the apex bends downward slightly. The 

 ratio of the enamel crown to the whole tooth varies considerably, 

 being equivalent to less than one-third of the total length on the 

 largest teeth and about one-half on the smallest. Near the anterior 

 end of the series the croAvns (pi. 8, figs. 2, 5, 7) are more noticeably 

 compressed in an anteroposterior direction at the base, their apices 

 are more attenuated, and the inward curve is less pronounced than 

 on the posterior teeth. The crowns of the teeth (pi. 8, fig. 3) from 

 near the posterior end of the middle portion of the series are rela- 

 tively short, robust, and their apices are acute and curve strongly 



'- Cor.ianovic? Krambeicrer, D.. Dc fossilibus Cetaceis Croatiae et Carneoliaa Rad jugo- 

 slavenske akademije znanosti i um.iptnosti, Zagreb, vol. Ill, pi. 1, flgs. 5, 5a, 6. 1892. 



'2 I'app, C. von, Heterodelphis leiodontus nova forma aus den Mioceuen Schichten dea 

 Comitates Sopron in Ungarn. Mitteil. .Tahrbuche Kfinigl. Ungar. Geol. Anstalt, Buda- 

 pest, vol. 14. Heft 2, text fig. 8. pi. 5, 1905. 



'* True, F. W., Description of a new fossil porpoise of the genus Delphinodon from tht 

 Miocene formation of Maryland. Journ. Acnd. Sci. Philadelphia, ser. 2. vol. 15, pp. 

 171-174, pi. 19. figs. 1-2: pi. 26. December 9, 10t2. 



