412 0. O. Marsh — Description of Miocene Mammalia. 



horizon, too, may now be sharply defined. The deposits 

 containing the remains from New Jersey here described, and 

 other vertebrate fossils obtained by the writer at the same or 

 adjoining localities, form a well-defined stratum resting uncon- 

 formable upon the Eocene greensand marls of Monmouth 

 county, 1ST. J. These Miocene deposits may be called the 

 Ammodon beds, from the largest land animal hitherto found in 

 them. So far as at present can be determined, this horizon 

 corresponds most nearly to that in the Rocky Mountain region 

 in which Ammodon oathrodon has been found. This subject 

 will be discussed by the writer in a later communication. 



Yale University, New Haven, Conn., October 24, 1893. 



Explanation of Plates. 



Plate Vir. 



Figure 1. — Skull of Protoceras celer, Marsh ; seen from above. 



Figure 2. — The same skull ; seen from below. Both figures one-half natural size. 



a, depression in maxillary ; /, frontal ; h, horn-core ; m, first molar ; 



ii, posterior nares; o, orbit; p, parietal; pm, second premolar; s, 



suture between frontal and parietal. 



Plate VIII. 



Figure 1. — Skull of Elotherium crassum. Marsh; side view. 



Figure 2. — The same skull; seen from above. 



Figure 3. — The same skull ; front view. These figures are one-eighth natural size. 



a, angle of lower jaw ; 6, protuberance on margin of lower jaw ; 



c, process below canine; /, frontal; m, malar process ; mx ) maxillary; 



n. nasal; j?, parietal; pm, premaxillary ; s, squamosal. 

 Figure 4. — Left fore foot of Elotherium crassum ; front view. 

 Figure 5. — Left hind foot of same species; front view. Both figures are one- 

 sixth natural size. 



a. astragalus; c, calcaueum; R, radius; U, ulna; II-V, digits and 



remnants of digits. 



Plate IX. 



Figure 1. — Skull of Elotherium clavum, Marsh, with brain-cast ; top view. 



About one-fifth natural size. 

 Figure 2. — Fourth lower premolar of Ammodon Leidyanum, Marsh. One-half 



natural size. 

 Figure 3. — Last lower molar of same species. Also one-half natural size. 

 Figure 4. — Last lower molar of Ammodon bathrodon, Marsh. One -half natural size. 



Plate X. 



Figure L. — Last upper molar of Perchoerus antiquus, Marsh. Natural size. 

 Figure 2. — Left lower jaw of Colodon luxatus. Marsh; side view. One-half 



natural size. 

 Figure 3. — The same jaw ; seen from above. 



Figure 4. — Last lower molar of Rhinoceros matutinus, Marsh. One-half natural size. 

 Figure 5. — Portion of lower jaw of Laopithecus robustus, Marsh. Natural size. 



