ANATOMY OF MEGAPTERA LONGIMANA. 99 



Seen from below, the processes, from the 2nd backwards, are concave 

 as far out as the beginning of the costal fossa, though very shallow 

 after the 9th. In Megaptera, after the 5th, the processes appear 

 convex below from the upturning of the process and the far in posi- 

 tion of the costal fossa. The form of the processes is further noted 

 with the breadth. 



Length, Breadth, and Thickness of the Dorsal Transverse Processes. 

 In length, the processes increase to the 13th, and begin to diminish after 

 the 14th. In thickness (vertical measurement, taken at the middle), 

 the 5th is much the greatest, behind which there is rapid diminution. 

 In breadth, which is their most remarkable character, they increase 

 backwards to the llth (7^ inches), and then diminish backwards. 

 The expansion is rapid on the 6th (breadth, 6 inches). From the 

 7th to the 14th the difference is not great. From the 9th to the 

 13th there is almost no difference in the breadth of the neck of the 

 process (about 4^ inches). On the llth the wing is within about an 

 eighth part of being twice as broad as the neck ; and from the 7th 

 to the llth the breadth of the wing is within inch of being as great 

 as the length of the body. The anterior intertrans verse projection, 

 or angle, marking off the two stages of the process, is about the middle 

 of the border. The projection on the posterior border is internal to 

 the middle, is well enough seen on most of the processes, and gives 

 the undulatory form to this border. The anterior half of the wing is 

 thin. The beam of the process runs out from the neck to opposite 

 the costal fossa, which it supports. The expansion on one side of the 

 process tends to alter its direction, compared with that of a process 

 which has the beam only. In the articulated skeleton, the spaces 

 between the processes, from the 6th backwards, are, between the 

 necks, about equal to the breadth of the neck ; between the wings 

 they average about 1| inch, being less than a fourth part of the 

 breadth of the processes. That this remarkable expansion of the 

 outer half of the dorsal transverse processes in B. musculus, com- 

 pared with Megaptera, is not merely a distinction of age is evident 

 from the fact that, while in this B. musculus the anterior border of 

 the wing has the appearance of a part from which a strip of cartilage 

 has been removed, the anterior border in Megaptera has already a 

 finished appearance. 



Costal Fossae. The costal fossae are very different from those of 

 Megaptera. They are most characteristic from the 6th to the 10th. 

 They are placed on about the posterior half of the broad end of the 

 process, rather than below it, and are elongated antero-posteriorly. 

 (On the 7th, length, 4 inches ; vertically 3 inches ; depth, inch.) 

 A rounded-off angle below gives the fossa a low triangular form, 

 changing to the elliptical as we go back from the 9th and 10th. The 

 overhanging arched upper boundary has very little of the obliquity 

 seen in Megaptera. The whole outer margin of the broad wing has 

 a gently sigmoid form, the posterior half, or a little more, above the 

 costal fossa. The fossa3 look mainly outwards, with a lesser degree 

 of direction backwards and downwards. The outer margin of the 

 processes, though not fully ossified, are much sharper than in Megap- 



