676 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 57. 



described as having four planes in an unworn condition. The 

 measurements, however, differ considerably. The jaw is very long 

 and slender and displays a diastema nearly equal in length to the 

 molar [=molar-premolar] series. The canine is rather small and 

 is separated from the incisors by a diastema of fourteen millimeters. 

 The second pair of incisors is nearly horizontal. Ventrally the 

 symphysis is evenly convex and is contracted to a round heel." 



Measurements (after Brown) — mm. 



Length of diastema 89 



Length of molar series (=cheek-tooth series) 91 



Depth of symphysis 18 



Width of jaws at narrowest constriction 21 



Brown's definition of this form seems sufficiently diagnostic to 

 distinguish it from all other species of the genus. Its comparatively 

 superior length of symphyseal and incisive portions, which indicates 

 an extremely long-nosed form, alone make it readily recognizable. 

 I therefore have proposed for this type the name Mylohyus hrowni. 



The second specimen, designated as " Mylohyus sp. b." (No. 

 11814), I regard, as suggested by Brown, probably the male phase 

 of the species just described. The third symphysal portion, desig- 

 nated by Brown as ^''Mylohyus sp. c," however, has all the charac- 

 teristics of the Platygonus group and I believe should be referred 

 to that genus. 



MYLOHYUS EXORTIVUS, new species. 



Type. — Lower jaw, nearly complete, containing the entire denti- 

 tion of both sides ; and. five upper cheek-teeth, p^ to m% of the righl 

 side (Cat. No. 8876, U.S.N.M. Coll.). 



Locality. — Cumberland Cave deposit, 4 miles northwest of Cum- 

 berland, Maryland. 



Diagnosis. — About the size of or perhaps somewhat smaller than 

 M. nasuttos (Leidy), and apparently differing from that species in 

 (1) the modifications of the canines, which seem to be relatively 

 wider in cross-section and almost entirely lacking the longitudinal 

 ribbing so characteristic of these teeth in M. nasutus; (2) the form 

 of the third upper premolar (the only tooth which can at present be 

 directly compared) which is proportionately broader, while the sec- 

 ondary cuspules are much less prominent; and (3) the relative dis- 

 tance between the cheek-tooth rows of the opposite sides, which is 

 much greater than in the type of Leidy's species. 



A second specimen (Cat. No. 8160 U.S.N.M. Coll.), consisting of 

 three milk molars and the first true molar of the right side (see 

 fig. 13), seems to belong to this species, although the first molar, 

 which is entirely unworn, is much narrower than the corresponding 

 tooth in the fully adult type specimen. This difference, however, 



