The baculum is the bony part of the penis. In the species of the subgenus Neotamias the proximal part of the baculum is termed the shaft, and the distal upturned part is termed the tip. On the dorsal side of the tip there is a longitudinal ridge termed the keel. The proximal end of the shaft is termed the base (see fig. 19). Depending on the species, the shaft varies from 2.11 to 5.28 mm. in length, and the base may or may not be widened or deepened. The purpose of this report is to: (1) Show th

The bacula which were borrowed from the University of Michigan, Museum of Zoology, were processed according to the method described by Friley (1947:395-397), whereas all others were processed according to the method described by White (1951:125). Thus the bacula that were borrowed from the University of Michigan, are maintained there in a separate collection, whereas the bacula borrowed from other museums and those that are at the University of Kansas, Museum of Natural History, are housed with

Individual variation. —Individual variation is small. This is shown by a coefficient of variability of only 3.85 in the length of the shaft in a series of 12 specimens of E. umbrinus umbrinus from Paradise Park, 21 mi. W and 15 mi. N Vernal, 10,050 ft., Uintah County, Utah. Variation with age. —In the chipmunks the baculum varies but little with age. In the youngest specimens that I have taken, the M3 and m3 have not yet erupted and there is no wear on P4 and p4; nevertheless, the baculum in the

Eutamias alpinus (Merriam) Figure 1 Pelage silky; tail bright orange beneath; markings relatively obscure; size small; skull broad, flattened, and large in proportion to body. Baculum: Shaft thin; keel low, 1/7 of length of tip; tip 39 per cent of length of shaft; angle formed by tip and shaft 135°; distal 1/3 of shaft slightly compressed laterally; base slightly wider than shaft; shaft short, 2.17 mm. Differs from E. speciosus , E. panamintinus , E. umbrinus , E. palmeri , and E. bulleri , in b

In California, Johnson (1943) recognized ten species of chipmunks and assigned these to the five main groups of species which were proposed by Howell (1929). In characterizing each species, Johnson ( op. cit. ) not only made a careful study of skins and skulls, but also employed many ecological data. Study of the bacula of the Californian chipmunks supports Johnson's ( op. cit. ) conclusion that there are ten species, but suggests that there are three (not five) groups of species in California—a

Friley, C. E., Jr. 1947. Preparation and preservation of the baculum of mammals. Jour. Mamm., 28:395-397, 1 fig., December 1. Howell, A. H. 1929. Revision of the American chipmunks (genera Tamias and Eutamias ). N. Amer. Fauna, 52:1-157, 10 pls., 9 maps. Johnson, D. H. 1943. Systematic review of the chipmunks (genus Eutamias of California). Univ. California Publ. Zool., 48:63-148, 6 pls., 12 figs, in text, December 24. White, J. A. 1951. A practical method for mounting the bacula of small mammal