222 PROCEEDINGS OP THE ACADEMY OF 



tus. He gave a list of the Ts^ovth American Mastodons, referring 

 them to the two groups characterized, tlie one by the continuous 

 cross-crests divided by a fissure only, the other b}' the transverse 

 series of two or more deeply separated tubercles. To tlie first 

 he referred 31. ohioficus.i Cuv.,and 31. pi'oavus^ Cope; to the second 

 31. chapmanii., Hays (from which 31. obi^ciirus could not he at 

 present distinguished), 31. shepardii, Leidv; 31. andium, D'Orb. 

 (the last two referred by Leidy to 31. obscurua) ; 31. mirifictis, 

 Leidy (closely allied to 3L humboJdfii), and 3T. pi-oductu.^., Cope. 



No question as to the distinctness of the 31. productua coidd 

 arise, although our knowledge of the 31. chapmanii to which it 

 has been referred is very slight. As described by Drs. Hays and 

 Leid^^, tiie lateral tubercles of the molars in that species are 

 closely appressed or not separated, being sometimes continuous 

 across the crown of the tooth. This description applies to one 

 of the specimens (a cast) selected by Dr. Leidy as his type, and 

 to a second specimen referred by him to the 31. andium. The 

 second tj^pe specimen of Leid}', a fragment of a posterior molar, 

 is undistinguishable from corresponding pai'ts of 31. andium. The 

 3L i^hepardii as described by Leidy is evidently quite distinct from 

 both tlie preceding and from the 31. productuM., in the absence of 

 accessory tubercles of the lateral principal cusps of the molars. 



The 3T. productus was characterized as follows : 



The posterior inferior molar supports five transverse series of 

 tubercles, of which the posterior is less developed than the others. 

 Each series is composed of two cusps of a conic form Avhich are 

 separated deeplv from each otlier, and are not united at the base 

 so as to become confluent on attrition. The cones of the outer side 

 support one or two accessory tubercles on a line with their inner 

 or median face, so that tlie transverse section of a worn tooth with 

 the two accessory cusps is that of a trefoil with the lobes iuwartls. 

 The penultimate molar in the same jaw supports three transverse 

 series. The symphysis is elongate depressed and subsimtulate ; 

 its proximal half is excavated, the distal half flattened. Two 

 tusks project from the extremity ; they are short, obtuse, and 

 flattened on the inner side. Total lengtli of a specimen which is 

 entire from the end of the symphyseal tusks to just beiiind tlie 

 last molar, 29 inches; length to first molar (penultimate), 19 

 Inches; length of first molar, 4.25 inches; of last molar, 6..^ inches; 

 width of same, 3 inches. Width across the rami at end of last 

 molar, 18 inches; do. between anterior borders of first molar, 2. .5; 

 do. of symphyseal spout, least, 4.5 inches; at base tusks, 4.75 

 inches. Length of free portion of S3'mphyseal tusks, 4 inches ; 

 diameter of do. 1.75 inches. 



Prof. Cope also described a species of Rodent from the same 

 beds under the name of Sleneofiber pansus. 



The molar teeth exhibit a regular gradation in width from the 

 large anterior to the small posterior. In the mandibular series 



