and the general similarity to the heteromyids appear as points in common between the two skulls, and demonstrate the closeness of Florentiamys to the heteromyids. However, the specimen does not contribute anything new to use in choosing between Wood's first two postulates. In the writer's opinion the undivided internal cingulum is a primitive condition that has survived in Florentiamys and Heliscomys tenuiceps. This common character together with the laterally compressed rostrum leads me to think that structurally, H. tenuiceps is a link between Florentiamys and the ancestral form of Heliscomys. Admittedly P4 of Florentiamys seems far from the Heliscomys pattern, but I think that this highly specialized structure could have been derived from Heliscomys or a common ancestor.

LITERATURE CITED

McGrew, Paul O.

1941. Heteromyids from the Miocene and Lower Oligocene. Geol. Ser. of Field Mus. Nat. Hist., vol. 8, pp. 55-57, 1 fig.

Wood, Albert E.

1933. A New Heteromyid Rodent from the Oligocene of Montana. Jour. Mamm., vol. 14, pp. 134-141, 5 figs.

1935. Evolution and Relationship of the Heteromyid Rodents with New Forms from the Tertiary of Western North America. Annals of the Carnegie Mus., vol. 24, pp. 73-262, 157 figs.

1937. Part II. Rodentia, in The Mammalian Fauna of the White River Oligocene; by William Berryman Scott and Glenn Lowell Jepsen. Trans. Amer. Phil. Soc., n.s., vol. 28, pp. 155-269, figs. 8-70, pls. 23-33.

1939. Additional Specimens of the Heteromyid Rodent Heliscomys from the Oligocene of Nebraska. Amer. Jour. Sci., vol. 237, pp. 550-561, 11 figs.

Transmitted March 1, 1948.

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