ANATOMY OF MEGAPTERA LONGIMANA. 89 



(at the 7th, depth 2|- inches, width iu front 3 inches; at 10th dorsal, 

 depth 1 inch, width in front U) to the 15th dorsal (depth f, width 

 in front f ) ; after the 3rd kimbar it begins to widen a little (at the 

 11th, depth I, width 1 inch). All along, the fossa between the in- 

 ternal and the great process, about ^ inch deep, will scarcely receive 

 the little finger. The sharp line from the low bifurcation of the 

 anterior border of the spinous process runs to this internal process, 

 from the 6th dorsal backwards.] 



16. Posterior Articular Processes. — After the 5th dorsal 

 there is no posterior articular surface bearing the appearance of 

 having supported cartilage. The process, better developed in 

 the other two finners, is represented by the backward projec- 

 tion where the ridges into which the posterior border of the 

 spine bifurcates join the diverging lamina, internal to the 

 anterior and upper part of the great anterior processes. 



The sloping triangular space included between the bifurca- 

 tion of the posterior border of the spine and the neural arch, 

 begins higher and is much broader than in the other two 

 finners. In regard to this character Megaptera and B. mus- 

 culus may be compared at the 4th lumbar, at which the angle 

 formed by the spine is the same in both, and where the neural 

 canal is the same in width (3f inches) and only I inch lower 

 in Megaptera (3j) than in B. muscuhis. In Megaptera the 

 bifurcation begins 6| inches above the body and 1^ behind the 

 vertical plane of the posterior end of the body ; in B. musculus, 

 5 1 above the bod}' and | inch behind the same vertical plane. 

 The triangular space in Megaptera is over 1 J inch in breadth 

 at the middle and shallow ; in B. musculus about 1 inch and 

 deeper. The contrast increases as we go back, while the trian- 

 gular space becomes narrower in both. In Megaptera, at the 

 same time, the posterior articular " process " becomes more pro- 

 jecting, back to the 9th lumbar. 



On the last lumbar and two first caudal there is a decided 

 triangular mesial projection above the beginning of the bifurca- 

 tion. It is at this limited region where the minor anterior 

 articular processes exist, and in the fossa between the latter is a 

 low median ridge, not present anywhere else in Megaptera, or 

 at any part in the other two finners. On the last lumbar and 

 three first caudal, where the triangular space between the pos- 

 terior articular processes runs into the roof of the neural canal. 



