THE SEA OTTER IN THE EASTERN PACIFIC OCEAN 33 



Figure 15. — Plastic impression of pelage sheared near skin surface from 

 midback of adult male sea otter D22-57. Anterior at right. Variation in 

 the diameter of guard hairs is demonstrated and their characteristic scale- 

 pattern. Magnification ca. X 75. (VBS 5718) 



mm. from the skin, the cross section is oval, slightly wavy in outline, and 55 

 to 67 microns (average 63) in diameter. The shaft of each smaller guard hair 

 has a small blade. The cross section of the smaller guard hair at the 10 mm. 

 level is 23 to 56 microns (average 42) in diameter. All guard hairs are 

 medullated. Near the surface of the skin, the guard hair root is often dis- 

 placed from the anterior side of the bundle by pressure of the underfur roots. 



The cross section of the underfur hair at the 10 mm. level is irregularly 3- 

 or 4-sided (fig. 18). In this respect it resembles the underfur of the land otter 

 (Lutra) (Wildman, 1954, fig. 98b). The underfur shaft is about 7 to 8 microns 

 in cross section diameter, only slightly greater than the root. 



In general, the pelage of the sea otter is similar to that of the land otter. 

 The guard hairs seem to be scarcer and more variable in size than those of the 

 land otter, though I have not made a quantitative comparison. The remark- 

 able arrangement of hairs in bundles, outside of which there are no isolated 



