Return this book on ortlieTore the Latest Date stamped below. A charge is made on all overdue books. University of Illinois Library M32 ZOOLOGICAL SERIES OF FIELD MUSEUM OF NATURAL HISTORY Volume XX CHICAGO, DECEMBER 31, 1938 No. 35 A NEW WOODRAT FROM MEXICO BY WILFRED H. OSGOOD CHIEF CURATOR OF ZOOLOGY A small collection of mammals obtained for .Field Museum by the well-known collector W. W. Brown, in the vicinity of Chilpan- cingo, Guerrero, Mexico, includes a series of 21 specimens represent- ing an undescribed subspecies of the little known genus Hodomys. This genus, characterized by Merriam in 1894, has not been reported since that time. Moreover, the two species referred to it, vetulus and alleni, are known only from their respective type localities, one in eastern and the other in western Mexico. The discovery of a third form, therefore, is of considerable interest.1 For the loan of specimens from the original series of Hodomys vetulus acknowledgment is tendered the United States Biological Survey, as represented by Dr. H. H. T. Jackson. Hodomys vetulus elatturus subsp. nov. Type from Chilpancingo, Guerrero, Mexico. No. 47442 Field Museum of Natural History. Adult male. Collected September 30, 1937, by W. W. Brown. Orig. No. 118. Characters. — Similar in size and cranial characters to Hodomys vetulus, but tail shorter and coloration of under parts paler; color of sides not extending to under parts; forehead and head in general more grayish. Color of type. — In a somewhat worn pelage, the upper parts are mainly clear Ochraceous Tawny, rather darker and richer than in specimens of vetulus examined. Head mainly grizzled Neutral Gray to bases of ears, somewhat mixed with fulvous between ears and on lower cheeks; under parts whitish buff modified laterally by dark under color and medially by self-colored light hairs; feet white; tail bicolor. 1 Since this was written, a subspecies of alleni has been described from Acapulco under the name guerrerensis by Goldman (Journ. Wash. Acad. Sci., 28, p. 498, Nov. 15, 1938). No. 431 475 476 FIELD MUSEUM OF NATURAL HISTORY— ZOOLOGY, VOL. XX Cranial characters. — Skull closely similar to that of vetulus, differing mainly in having the nasals more compressed or narrowed posteriorly with their endings usually even with those of the premaxillae. Measurements. — Average of four adult topotypes measured by the collector: total length 347 (330-365) ; tail vertebrae 149 (140-155) ; hind foot 35. Skull of type: greatest length 45.1; basilar length 37; zygomatic breadth 23.8; mastoid breadth 17; interorbital constriction 15.4; length of nasals 17; palatine foramina 8.5x2.6; cheek teeth (crowns 8.7, alveoli 9.4). Remarks. — In comparison with two paratypes of H. vetulus from Tehuacan, Puebla, the western series tends to be somewhat more grayish throughout and the extension of fulvous to the head and under parts is considerably less. The head, which in vetulus is mainly gray only on the sides, is almost wholly so in elatturus, extending dorsally at least to the interorbital region and the base of the ears. In several specimens the hairs of the midventral line and inguinal region are wholly soiled whitish to their bases. The rather close resemblance to vetulus favors the assumption that the form here described may be no more than a geographic race. Although intermediate localities are yet to be heard from, this close resemblance seems best indicated by the subspecific status. THE U3RARY OF THE JAN 3 01939 UNIVERSITY OF ILLINOIS