2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I49 



while collecting in the Knight and New Fork members of the Wasatch 

 formation in southwestern Wyoming during various field seasons 

 since 1948. 



ACKNOWLEDGMENTS 



Although the present study is based principally on the Menisco- 

 therium remains in the U. S. National Museum, the work has been 

 advanced immeasurably through the courtesies extended by various 

 universities and other museums in permitting access to related com- 

 parative materials and in lending certain types and representative 

 specimens for further study in Washington. 



Drs. Glenn L. Jepsen and Donald Baird aided particularly in 

 allowing me to study Phenacodus skeletal material in the Princeton 

 collections and in furnishing me with a cast of the dentition belong- 

 ing to a well-preserved specimen of Meniscotherium found near 

 Moneta in the Wind River Basin. Drs. Edwin H. Colbert, Bobb 

 Schaeffer, and Malcolm C. McKenna have been of much assistance in 

 the study of related condylarth materials in the American Museum, 

 particularly in lending me foot material of Phenacodus, Tetra- 

 claenodon, and Hyopsodus. Dr. Joseph T. Gregory, while at Yale 

 University, arranged for me to borrow the type of Meniscotherium 

 robustum from Wyoming, and Drs. Elwyn L. Simons and John H. 

 Ostrom made available for this study the "Hyracops socialis" foot 

 material and a newly prepared skull of Phenacodus. I am indebted 

 to Dr. Tilly Edinger for turning over to me for study endocranial 

 casts of Meniscotherium, Phenacodus, and Periptychus, and to Dr. 

 Clayton E. Ray for arranging the loan of these materials from the 

 American Museum and the Museum of Comparative Zoology collec- 

 tions. Drs. Rainer Zangerl and William D. Turnbull forwarded to 

 me for study the Chicago Natural History Museum specimens of 

 Meniscotherium from western Colorado and graciously permitted me 

 to review the associated mammalian collections for environmental 

 indications. Dr. Craig C. Black lent me for inclusion in this study 

 the Carnegie Museum specimens of Meniscotherium from the Colo- 

 rado area, collected by Earl Douglass. 



Dr. George G. Simpson early expressed an interest in making a 

 study of Meniscotherium (see Gazin, 1952, p. 61) as a result of 

 his extensive collection for the American Museum of materials repre- 

 senting the San Juan Basin population. Since moving to Cambridge, 

 however, he has indicated with regret the improbability of his carry- 

 ing out this study in the near future. His deferring to my interest in 

 this undertaking is much appreciated. 



