ANATOMY OF MEGAPTERA LONGIMANA, 87 



development of the upper posterior corner partly carries the process 

 backwards to opposite the fore part of the spinous process, but in 

 Megaptera it is mainly the greater length of the lamina which makes 

 the articular process seem so far in front of the spine. The develop- 

 ment of the anterior-inferior corner in B. musculus, bringing the 

 lower border so low as almost to form a right angle with the pedicle, 

 renders the intervertebral notch very low, the anterior part scarcely 

 2 inches above the level of the body, while in Megaptera the same 

 measurement is about 3 inches. 



After the 1st lumbar, the processes become less quadrate, and 

 more like those of Megaptera, the lower anterior corner rounded off', 

 and, after the 5th lumbar, reduced to a mere convexity. After the 

 14th lumbar, the pedicle and the process form an uninterrupted con- 

 cave border, going up to the blunt point of a triangular process. The 

 6th, 7th, and 8th caudal are directed up, with a little concavity on 

 both borders. From the 9th backwards, the short bluntly triangular 

 processes have a direction rather backwards. But all along the 

 lumbar and anterior caudal regions, the posterior angle remains 

 nearly a right angle, and the upper boi-der has very little convexity. 

 In the caudal region, the processes become much thicker, increasing 

 to the 9th, where the thickness is li inches. 



In width-ajmrt, the distance falls, from the 1st to the last dorsal, 

 from 10 inches to 2|. At the 10th lumbar it has increased to 3|, 

 and from this vertebra, backwards, the width-apart of the articular 

 processes is greater in B. musculus than in Megaptera. (Compare 

 Tables II. and III.)] 



15. Internal or Lesser Anterior Articular Processes. 

 — These processes, so well developed in B. musculus, are present 

 here only on the last lumbar and three first caudal vertebrse, 

 and only to a rudimentary extent. On the 2nd caudal, where 

 they are best marked, they project about ^ inch, and have a 

 vertical base of about 1| inch, the triangular fossa between 

 them "I inch deep and f inch wide in front. On the 3rd caudal 

 they are only low ridges, on the 4th all trace of them is gone, 

 giving a wide uninterrupted space between the great articular 

 processes. On the 1st caudal they are nearly as well developed 

 as on the 2nd, with wider interval between them ; on the last 

 lumbar they are less marked, and faint traces of them exist 

 along the trunk vertebra?. 



To interpret these processes, begin at the 6th dorsal vertebra, 

 the most posterior of those presenting an articular socket. The 

 outer and inner edges of that socket are represented on the 

 vertebrfp. behind by two lines, one, now the sharp one (sharp 

 until the internal articular processes appear at the 10th lumbar), 



