1896.] NATURAL SCIENCES OF PHILADELPHIA. 383 



in. m. 



f longitudinal ; 9 



Diameters M. ^ ■{ anteroposterior ; 3.75 



(^transverse; 2.50 



( longitudinal ; 7.5 



Diameters M. ^ -j anteroposterior ; 3 



[ transverse ; " 2.2 



Miorotus speothen Cope. Proceeds. Amer. Philos. Soc, 1871, p. 87, fig. 13. Arvicola 

 (Pitymyg) tetradelta, 1. c, 1871, pp. 87-8, fig. 14. 



Arvicola tetradelta was founded on the M. i and ^ of an in- 

 dividual of smaller size than the types of A.speothen, but not other- 

 wise different. 



The species Microtus involutus from the Port Kennedy deposit is 

 allied to M. sigmodus, while M. didelfa is more nearly related to 

 M. pinetorum. 



CARNIVORA. 



TJrsus haplodon sp. nov. Ursus jiristinus Leidy, Cope, Proceeds. Amer. Philos. Soc, 

 1871, p. 96, not Arctodis priatinus Leidy, Proc. Acad. Philada., 185-1, 90 ; Holmes, 

 Postpliocene Foss. So. Carolina, 1860, 115, pi. xxiii, figs. 3-4. 



There are contained in the Academy's collection, remains of 

 thirty-six individuals of this large bear from the Port Kennedy fis- 

 sure, and parts of several others are included in the Wheatley col- 

 lection. Study of this material has led me to the conclusion that 

 Ursus pristinus of Leidy is a distinct though allied species. The 

 latter was founded on a single tooth, the first inferior true molar of 

 the left side. This tooth cannot now be found, but Leidy has given 

 a figure which is of much excellence from an artistic point of view, 

 and judging from other figures in the same Avork, is probably trust- 

 worthy, especially as it corroborates the description in every par- 

 ticular. I should have hesitated to distinguish the present animal, 

 however, had it not been that the Port Kennedy material includes 

 fourteen teeth from the same position in the jaw, three of which are 

 in the Wheatley collection. These all agree closely and differ 

 from Leidy's animal. 



Leidy notes that in U. pristinus the anterior width of the 

 tooth exceeds the posterior, and the figure confirms this statement. 

 In U. haplodon the extremities of the crown are of equal width. 

 The grinding surface of the crown is in U. pristinus rough with 

 tubercles, while it is smooth in U. haplodon. This character 

 might be supposed to be due to the attrition of use, but it is uni- 

 versal in the teeth of TJ. haplodon without regard to age. The 

 trigon in U. pristinus is triangular ; in U. haplodon it is a semi- 



