228 DISCOVERY REPORTS 



the hairs in two lines is thus similar to that frequently found in Fin whales, whereas 

 in Blue whales the presence of two lines has not been recorded. The number of hairs 

 on the ramus of the jaw on one side varies from five to eighteen and averages ten. 



The hair on the chin is arranged in two irregular vertical rows, the number of hairs 

 in the two rows frequently being equal and seldom differing by more than four or five. 

 The number of hairs on the chin varies from fourteen to forty-four and averages 

 twenty-eight. 



Table XI shows the occurrence of hair on the chin, mandible, and head in the 

 present series of Sei whales. 



VENTRAL GROOVES 



The arrangement of the ventral grooves in the Sei whale diflfers from that in the Fin 

 and Blue whales in that at their posterior extremity the grooves end evenly well anterior 

 to the umbilicus (PI. XVIII, figs, i and 2). No examples were recorded in which they 

 ran back as far as the umbilicus, and only one in which a median groove joined the 

 umbilicus and genital groove. The outside lateral groove sometimes runs into the 

 angle of the gape anteriorly. 



The number of grooves varies from forty to sixty-two, the average being forty-seven, 

 which may be compared with the corresponding figures of eighty-nine for Blue whales 

 and eighty-six for Fin whales. The smaller number of grooves in the present species is 

 correlated with its smaller size. Table XII gives the number of grooves recorded in 

 fifty-eight Sei whales. In the female two or three small subsidiary grooves are present 

 on each side of the mammary grooves. 



BALEEN 



The baleen of the Sei whale is characteristically of fine texture, and the reason for 

 this is apparent when the number of plates present and the size of the whale are 

 considered. The number of baleen plates on one side of the mouth averages 342 in this 

 species, nearly the same number as is found in Blue whales (average 348) and not 

 greatly fewer than that found in the Fin whale (average 363). As the size of the mouth 

 is very much smaller in the Sei whale than in the other species (the tip of the snout to 

 the angle of the gape averages about 2-9 m. in Sei whales, 4-25 m. in Blue whales and 

 4-0 m. in Fin whales), while the number of baleen plates is nearly the same, the texture 

 of the baleen is necessarily much finer (PI. XIX, fig. i). Table XIII gives the numbers 

 of plates present in one side of the mouth in thirty-seven Sei whales. 



The colour of most of the baleen plates is dark, nearly black, and the bristles at the 

 inner edges of the plates are white or greyish white and fine and silky in texture. At the 

 anterior end of the series, however, a number of white plates are frequently present, on 

 one or both sides. When the white spot on the anterior part of the margin of the upper 

 jaw, described above, is present, the white baleen plates are situated so that they hang 

 immediately below it. Table XIV summarizes the colour notes collected regarding the 

 baleen of Sei whales. Whale D. 119, landed at Durban, in which the baleen plates were 



