OF BAL^XOPTERA MUSCULUS. 221 



second and third. The first rib is flat and broad, the tubercle turns downward, presents a 

 small articular surface and sends inward a slight prominence representing the head and 

 neck. The angle is marked by an elevation which bends forward; the space between it 

 and the tubercle is convex in front and concave behind, which is the case also in the 

 succeeding ribs. The second rib has on the tubercle a narrow articular surface 4 1-2 

 inches long. The neck is slender, 4 1-2 inches long and terminates in a small knob for 

 the head. The angle bears a prominence which, unlike that of the first rib, bends back- 

 ward. The third rib is longer, but the head and neck measure only 3 inches. The angle is 

 more prominent. The neck of the fourth rib is indicated by a very slight prominence. 

 In the subsequent ribs there is no sign of it. The fifth and sixth resemble each other very 

 closely. The latter is the longer one, and the angular prominence is less well marked. There 

 is but a very slight downward projection from the articular tubercle. The succeeding ribs 

 present a similar gi-adual change ; the prominence at the angle is less and less, so as to be 

 hardly perceptible in the 12th. The ribs become narrower and the articulating surface 

 shorter and broader, so that the extremity of each of the four ribs preceding the last is al- 

 most globular ; in the fifteenth, however, it is oblong. This I'ib is flat, compressed above 

 and below, and extending directly outward from the vertebral column for 7 or 8 inches, 

 when, becoming narrower, it turns upon itself and points backward and downward, with an 

 external and an internal surface. It has, properly speaking, no angle. The eleventh and 

 twelth ribs present a small prominence on the posterior superior border, apparently for 

 muscular attachment. 



The following table gives the greatest length of each rib along the convexity, the dis- 

 tance between the ends in a straight line ; and, to show the amount of curvature, the great- 

 est distance from a straight line to the inner surface of the bone. (The measurements are 

 in inches.) 



1| ^ 



10 I 11 I 12 I 1.3 I 14 



15 



Gre.itest length. 

 Length in n straight 

 Amount of curve. 



41 64 70.75 

 33.537.5 47.5 

 8 12.2514.25 



74.5 173.25 



52.7556 



14.2516 



75 j74.25,71.5 ,67.75 

 57.25:58.25,54.75:53 

 16 16.25il5.75|l4.5 



63.25 



51.5 



13.25 



59.5 53.5 48 

 49.25 40.25,44 

 11.5 8.75 5.25 



46 

 43.5 



5.25 



47.5 

 45.5 

 6.25 



On comparing the heads and necks of the first four ribs with the woodcuts of those of the 

 Ro.sherville skeleton, it is plain that those of this whale are much more developed. The 

 third, though less developed than the second, is as much so as the second of the Rosher- 

 ville. 



The ribs of the right side. — The first five offer no peculiarity. The tubercle of the 

 sixth is rather heavier than that of the other side, and the tuberosity at the angle very 

 much so. A little external to the angle a rough prominence about 8 inches long projects 

 boldly from the upper part of the rib, giving very strongly the appearance of a repaned 

 fracture ; the continuity of the inferior edge, however, is perfect. The seventh bears a 

 corresponding, but less marked prominence. The tubercle of this rib is very rough and ir- 

 regular, as if by the efiects of inflammation. It is of double thickness, owing to the projec- 

 tion of an irregular mass from its posterior aspect. The tubercles of the eighth and ninth 

 have similar malformations, but in a less and decreasing degree. The shafts are regular. 

 The succeeding ribs are normal, till the fifteenth, which is a fine specimen of an ununited 

 fracture. The proximal fragment, 14 inches long, corresponds with a like extent of the rib 

 of the opposite side, except in being on a smaller scale and in running gradually to a point. 



MEMOIRS. B09T. SOC. NAT. HIST. VOL. II. 56 



