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University of California Publications in Geology [Vol. 10 



ISCHYROSMILUS ?2 IDAHOENSIS, n. sp. 

 Type specimen, no. 22343, from beds referred to the Idaho formation at 

 locality 3036C, near Froman Ferry on the Snake River in southwestern Idaho. 

 The type consists of the anterior two-thirds of the left ramus of a mandible 

 with the roots of all of the teeth. 



Specimen no. 22343 (fig. 1) represents a very large sabre-tooth 

 approximating the dimensions of the largest individuals of Smilodon 

 calif ornicus from Rancho La Brea. The Idaho specimen differs from 

 the typical 8. calif ornicus in dentition by the presence of a small Pg. 

 This tooth is found in a small percentage of the Rancho La Brea sabre- 

 tooth specimens, but is normally absent. The Idaho mandible differs 



Fig. 1. Ischyrosmilus ? idahoensis, n. sp. Outer and superior views of man- 

 dible. Type specimen, no. 22343. X %. From beds referred to Idaho formation, 

 near Froman Ferry, Idaho. 



from that of S. calif ornicus very decidedly in the size and proportions 

 of the flange below the diastema. In S. calif ornicus the flange is com- 

 paratively short, ending posteriorly rather abruptly some distance in 

 front of Pj. In no 22343 the posterior end of the flange fades out 

 below the anterior end of P 5 . A flange of the type seen in the Idaho 

 specimen is found also in Ischyrosmilus ischyrus of the Tulare Pliocene 



- Ischyrosmilus, new genus, founded upon Machaerodus? ischyrus Merriam. 

 Genus characterized as follows: mandible massive; flange clearly marked, 

 relatively wide anteroposteriorly, slightly wider than in Smilodon, not as strongly 

 developed as in Machaerodus ; diastema much as in Machaerodus but shorter than 

 in Smilodon. P5 very small with one root. Pj with single posterior cusp or 

 incipient division of this cusp. For more extended discussion, see Merriam, J. C, 

 Tertiary Mammalian Faunas of the Mohave Desert Region, Univ. Calif. Publ., 

 Bull. Dept. Geol., in press. 



