80 PROFESSOR STRUTHERS. 



Looking to the direction of these lateral openings, their 

 general tendency is seen to be downwards, the sharp boundary 

 above, the grooved side below. This is plainly seen in the lower 

 series and on the middle series where they are single. When 

 they become double, in the chevron region, the posterior foramen 

 is directed also backwards, the anterior one forwards. The 

 forward and backward direction is more marked on the upper 

 series. On some a shallow groove is seen to pass between the 

 middle and the upper series. The position of the sharp and the 

 grooved sides of the great foramina of the vertical passage 

 accord with the upward course of the passage. 



[Vertical Passage and Foramina in B. musculus. The position of 

 these foramina would be sufficient to distinguish B. musculus from 

 Megaptera. The loiver stage of the passage is present on the llth 

 caudal vertebra as a half-oval notch in the haemal ridge ; on the 1 2th, 

 13th, and 14th as a foramen. The middle stage is present as a fora- 

 men in the transverse process from the 7th to the 13th, the three 

 anterior of these in the process proper, the three posterior between 

 the process and the side of the body. In the 7th the foramen is 

 large, If by If inch ; the bar of bone in front of it 1 inch broad. In 

 the 6th, there is a deep notch in the front of the transverse process 

 instead of a foramen. On the 14th, the middle stage opens high on 

 the body, and behind the 14th it opens at the top. The upper stage on 

 the 12th and 13th is present as a.notch; on the 14th (the last com- 

 plete neural arch) as a foramen on the right side, as a notch on the 

 left; on the 15th and 16th, as a foramen on both sides; on the 17th 

 to the 20th, as an open fissure crossing the middle line between the 

 upper apertures of the second stage; on the 21st, 22nd, and 23rd, a 

 septum intercepts this fissure in the middle line. 



The great breadth of the transverse processes in B. musculus ac- 

 counts for their being perforated so far forwards as on seven vertebra? 

 anterior to the first one (the 14th) in which the second stage of the 

 passage is roofed over. The apertures of the passage (judging by the 

 upper apertures of the second stage) are of about the same size and 

 form as in Megaptera, except those in the 8th, 7th, and 6th trans- 

 verse processes which are larger, the 7th admitting the forefinger, the 

 Gth admitting three fingers.] 



