1892.] NATURAL SCIENCES OF PHILADELPHIA. 227 



and widely notched, terminating on each side in a subequihateral 

 angular prominence. Both carapace and plastron are without 

 sculpture, the posterior angles of the plastron onl}' being longitudi- 

 nally grooved below. The vertebral scuta are considerably wider 

 than long, as is also the anal scutum. Both carapace and plastron 

 are very thin, not exceeding one-quarter inch in the specimen 

 described, except at the borders. Measui*ements : Length over all 

 4-2 feet; width over all 4 feet ; width of penultimate dorsal scute 

 1-275 feet, length '85 feet ; width of last vertebral scute 1-35 feet ; 

 width of anal scute 1-5 feet, length -6 feet. Length of penultimate 

 costal scute -9 feet ; length of last costal -95 feet. Width of lip of 

 plastron at base '8 feet ; width of anterior lobe at axillae 2 feet. 

 Width of posterior lobe of plastron at base 2 feet ; width at fundus 

 of median notch 1-1 feet ; Avidth at apices of angular processes '85 

 feet ; depth of notch -5 feet. This is the largest species of land 

 tortoise yet known from North America. 



EDENTATA. 



Megalonyx, sp. 



Teeth and fragments of skull. 



CARNIA'ORA. 



A canid and three undetermined forms represent the Carnivora. 



PROBOSCIDIA. 

 Mastodon successor, sp. nov. 



This species is represented by teeth in collections previously made 

 by Prof Cummins, and though the characters of these resemble 

 closely those of the Tetrabelodon angustidens, I did not identify them 

 as pertaining to that species. From its association with the genus 

 Equus, I suspected that it would prove to be distinct from the latter ; 

 and the accession of more material proves this to be the case. It is 

 a species of the genus Mastodon and not of Tetrabelodon, having 

 a very short, contracted and elephant-like symphysis. The most 

 complete specimen is represented by both rami of the lower jaw 

 with symphysis complete, but lacking angles and condyles ; accom- 

 panied by a tusk of the upper jaw. The latter is without enamel 

 band. The second true molars are in place, showing their patterns, 

 and the third molars have only three crests protruded. Besides 



