446 PBOCEEDINGS OF THE ACADEMY OF [1894. 



A KEW INSECTIVORE FROM THE WHITE RIVER BEDS. 

 BY W. B. SCOTT. 



The American Tertiary formations have yielded a surprisingly 

 scanty insectivorous fauna. Many names have, it is true, been pro- 

 posed, but for the most part, these names have been given to such 

 fragmentary and uncharacteristic specimens, that they remain mere 

 nomina nuda. Only one family, the Leptictida', is at all well under- 

 stood, and the ancestors of even the peculiarly American recent types 

 are still quite unknown. 



During the past summer Mr. M. S. Farr, of the Chicago Univer- 

 sity Expedition to the White River bad lands of South Dakota, had 

 the good fortune to discover an insectivorous type new to the Ameri- 

 can Tertiary fauna, and representing an undescribed genus. For 

 the opportunity of studying and describing this very interesting spe- 

 cimen, I am indebted to the kindness of Professor Baur, to whom I 

 desire to express my very sincere thanks. 



The specimen consists of the facial region and mandible, Avith nearly 

 complete dentition, of a small animal, which upon examination, proves 

 to be a member of the family Soricidce, or shrews, though not alto- 

 gether agreeing with the definition of that family as usually given. 

 This is the first of the family to be found in any Tertiary horizon of 

 North America. 



The genus may be called Protosorex and is defined as follows: 

 Maxillary dentition much as in Sorex, hut with less reduced third 

 molar and smaller internal cusps on last premolar. Mandible with 

 four minute teeth between the molars and the large, procumbent 

 incisors. In all other known Soricidce the number of such teeth is 

 two, except in one species of Myosorex, which sometimes has three. 



The species, P. crassus, sp. nov., is characterized by the rather 

 short and broad face, vaulted palate, straight alveolar border, and 

 by the relatively large size. 



The type specimen is of an individual rather advanced in life, and 

 all the facial sutures have disappeared. The upper surface of the 

 fronto-nasal region is ^tiaighter, broader, and more flattened than 

 in the recent species of Sorex. The zygomatic arches have already 



