EXTERNAL CHARACTERS OF FIN WHALES 353 



whole mass of pigment slightly to the left side of the body, except inside the mouth, 

 where it predominates on the right. 



The junction of the ventral white area with the dorsal pigment is rather irregular, and in 

 places without any very definite line of demarcation. In the thoracic region the pigment 

 reaches down on each side in irregular projections over the outer ventral grooves 

 (see Plate XXXII, fig. 2, and Plate XXXIV, fig. i), which in places may be pigmented 

 in the actual grooves but white on the ridges. The degree to which it extends over the 

 grooves is variable, but the pigment on the left-hand side always reaches farther down 

 than on the right. The ventral white area may reach without interruption to the ventral 

 surface of the tail flukes, but frequently the pigmented area of the tail reaches farther 

 down behind the anus to meet in the mid-ventral line and cut off the white area just in 

 front of the flukes. At a point a short distance behind the anus there is on each side a 

 narrow projection of pigment which reaches downwards and forwards towards the anus. 

 These promontories may be so ill-marked as to be almost indistinguishable, or they may 

 be about a yard long and meet at the anus. In Plate XXXIII, fig. 2, one of these promon- 

 tories can be seen, but the other is obscured by high lights on the whale's skin. In 

 this whale the white ventral area extended well back to the tail flukes, while in Plate 

 XXXIII, fig. I, which was a heavily pigmented whale, almost the whole of the white 

 area behind the anus was obliterated by pigment. The rim of the pigment on each side, 

 from about the region of the genital aperture (or sometimes farther forward) back to 

 the tail flukes, may be fairly regular or may be broken up by a kind of mottled condition 

 suggestive of galvanized iron. 



In the head region the left mandible is pigmented externally while the right is white. 

 The outer edges of the baleen plates are all pigmented on the left side except for a 

 few at the extreme anterior end, which may or may not be white. On the right side 

 the anterior baleen plates, more than a third of the total number on that side, are 

 white. The rest are pigmented, and the demarcation is always sharp. The right upper 

 jaw is pigmented opposite the dark plates and is white opposite the unpigmented 

 plates. The left upper jaw is pigmented along the whole of its length. All these details are 

 illustrated in Plate XXXII, figs, i and 2, which show the right and left sides of the head 

 of the same whale. Inside the mouth the asymmetry of the pigmentation is reversed. 

 The inner side of the right mandible is pigmented while that of the left is whitish, 

 and on the tongue pigment is predominant on the right. Very little pigment is present 

 on the palate though a few pale streaks are usually visible at the posterior end and the 

 extreme anterior tip is sometimes pigmented. The bristles on the inside of the baleen 

 plates are all unpigmented. 



Certain light and dark streaks occur about the head and shoulders. There is always 

 a well-marked narrow pale streak reaching backwards from the ear, which is well seen 

 in Plate XXXII, fig. 2. It takes a slightly upward course at first and then turns down, 

 becoming more diffuse and fading near the insertion of the fiipper. There may also 

 be an indefinite and not very pronounced pale streak running upwards and backwards 

 from the axilla. There is regularly a V-shaped pale streak on the back. The apex of 



K IV 13 



