. Bulletin of the Department of Geology. Geology. 1919] Merriam: Tertiary Mammalian Faunas of Mohave Desert 543 ISCHYKOSMILUS Merriam Uo";;, strong; a-fitkr), knife. Machaerodus? J. C. Merriam, Univ. Calif. Publ., Bull. Dept. Geol., vol. 4, p. 171, 1905. Ischyrosmilus Merriam, Univ. Calif. Publ., Bull. Dept. Geol., vol. 10, p. 524, 1918. Type species Machaerodus? ischyrus Merriam from beds near McKittrick on the western border of the San Joaquin Valley, California. The type is known only by the mandible and inferior dentition. Mandible massive; flange clearly marked, relatively wi
. Bulletin of the Department of Geology. Geology. 1919] Merriam: Tertiary Mammalian Faunas of Mohave Desert 543 ISCHYKOSMILUS Merriam Uo";;, strong; a-fitkr), knife. Machaerodus? J. C. Merriam, Univ. Calif. Publ., Bull. Dept. Geol., vol. 4, p. 171, 1905. Ischyrosmilus Merriam, Univ. Calif. Publ., Bull. Dept. Geol., vol. 10, p. 524, 1918. Type species Machaerodus? ischyrus Merriam from beds near McKittrick on the western border of the San Joaquin Valley, California. The type is known only by the mandible and inferior dentition. Mandible massive; flange clearly marked, relatively wide anteroposterior^, slightly deeper than in Smilodon, not as strongly developed as in typical Machaerodus ; length of diastema much as in Machaerodus, but shorter than in Smilodon. P3 very small, and with one root. P4 with a single posterior cusp or with in- cipient division of this cusp. Mt without metaconid and heel. The group is known only from beds referred to the Fig. 154. Mustela? buwaldi, n. sp. Mandible with P, to M1; no. 21323, X 1%. Ricardo Pliocene, Mohave Desert, California. Ischyrosmilus differs from the Dinietis group in the absence of M2, absence of heel and metaconid of Mx, great reduction of P;j, and in the rela- tively large size of the flange below the diastema. From IIoptophone us it differs in the absence of heel and metaconid of M1; and in the somewhat greater anteroposterior diam- eter of the relatively shallow flange. From typical Machaerodus it differs in the greater reduction of P,, and in the greater antero- posterior diameter of the relatively shallow flange. From Smilodon it differs in the shorter diastema, larger flange, and more simple form of the posterior lobe of P4. This group is nearest Machaerodus, and may be considered as a subgenus under that division. The fact that two forms are found which resemble each other in the general char- acters through which they differ from other groups, though they are evidently different specifical
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