NEW PALEOCENE MAMMAI.S SIMPSON 



237 



Diagnosis. — Gidley: "About the equivalent of T. subtrigonus in 

 size but presents the following differences: (1) The teeth are more 

 massive, (2) the molars are relatively wider especially in the region 

 of the heel * * * (4) * * * ^j^g paraconid is * * * 

 more closely appressed to the metaconid * * * ". 



Simpson: P3-4 markedly heavier than in T. subtrigonus. Mi-2 

 similar but paraconid more internal and nearly confluent with 

 metaconid. M3 relatively shorter and wider. Measurements of 

 type in millimeters: 



Family MIACIDAE 



There are at least four very distinct species of miacids in the collec- 

 tion. One is poorly known and near Didymictis haydenianus, from 

 which it cannot properly be distinguished. Of the others, one cer- 

 tainly represents a new genus and the other two may be referred to 

 Didymictis, although sharply distinct from other species of that 

 broadly drawTi genus. 



ICTIDOPAPPUS,38 new genus 



Type. — Ictidopappus mustelinus, new species. 



Distribution. — Middle Paleocene, Fort Union, Mont. 



Diagnosis. — Differing from Didymictis in the relatively smaller and 

 much simpler P3.4 and relatively lower and longer trigonid of Mi, from 

 Viverravus in the wider and more triangular P4 and more definitely 

 basined talonids, and from other miacids in the absence of M3. P4 

 shorter than Mi but nearly as high, relatively wide, subtriangular, 

 not markedly trenchant, paraconid and metaconid barely indicated, 

 talonid very short, vaguely cusped, no other cuspules and no cingulum. 



ICTIDOPAPPUS MUSTELINUS.39 new species 



Type. — U.S.N.M. no. 9296, right lower jaw with P3-M1 and talon- 

 id of M2. Collected by A. C. Silberling. 



Horizon and locality. — Gidley Quarry, Fort Union, Aliddle Paleocene 

 horizon. Crazy Mountain Field, Mont. 



Diagnosis. — Sole known species of the genus as defined above. 

 Measurements of type in millimeters as follows: 



28 "IktIj, weasel+paTnros, grandfather. Also in analogy with Viverravus. 

 * Mxiitelinus, relating to or resembling a weasel. 



