0. C. Marsh — Discovery of Cretaceous Mammalia. 261 



the committee of publication, lie gave me full permission to 

 publish it separately, duly credited to the Academy, and a few 

 copies were thus printed, and sent to Europe. The sudden 

 death of Dr. Leidy delayed publication by the Academy, but 

 the paper appeared in the Proceedings, pp. 237-241. 1891, 

 essentially as presented, the main alterations being verbal 

 changes, the result of editorial supervision. Separate copies 

 had previously been printed by the Academy, and distributed 

 by me. 



Prof. Osborn next had his original review as offered to the 

 Philadelphia Academy published in full in the American 

 jSTaturalist for July, 1891, and with it my reply as presented to 

 the same Academy, except under a somewhat different title. 

 To the latter article, he prepared the rejoinder read before 

 the American Association at Washington, August 21, 1891, 

 published it in the American Naturalist for September, 1891, 

 and issued revised, separate copies. In this paper, Prof. 

 Osborn attempts to answer the criticism upon his review 

 and previous work on Mesozoic mammals, and repeats a 

 number of statements made in his original review, and since 

 shown to be erroneous. The value of such extensive publica- 

 tions without examination of a single specimen described may 

 be fairly questioned. The record of them above presented is 

 for the benefit of those especially interested in the subject. 



New Haven, Conn., Feb. 23, 1892. 



"Figure 1 

 Figure 2 

 Figure 3 

 Figure 4 

 Figure 5 

 Figure 6 

 Figure 7 



Explanation of Plates. 



Plate V. 



— Upper cutting premolar of Cimolomys gracilis, Marsh. 



— Upper molar of Tripriodon caperatus, Marsh. 



— Right upper molar of Tripriodon coelatus, Marsh. 



— Left lower incisor of Halodon sculptus, Marsh, in position in jaw. 



— Right lower fourth premolar of same species. 



— Worn molar of Dipriodon lunatus, Marsh. 



Right lower jaw of Dipriodon lunatus, with third and fourth premolars 



and first molar in place. Natural size. 



Plate VI. 



Figure 1 . — Upper incisor of Dipriodon lunatus. 



Figure 2. — Upper premolar of Nanomyops {Nanomys) minutus, Marsh. 

 Figure 3. — Upper molar of Cimolodon nitidus, Marsh. 



Figure 4. — Left lower incisor of Cimolodon parvus, Marsh, in position in jaw. 

 Figure 5. — Lower incisor of Selenacodon. 

 Figure 6. — Molar of Cimolodon parvus. 

 Figure 7. — Molar of Cimolodon nitidus. 



Figure 8. — Lower jaw of Cimolodon agilis, Marsh, with penultimate molar in place. 

 Figure 9. — Right lower jaw of Cimolodon nitidus, with cutting premolar and last 

 two molars in place. 

 Note. — In all the plates, Figure a is natural size. The figures enlarged have the 

 increase in size given in diameters over each cut. 



