26 PROFESSOR STRUTHERS. 



prominent part of the two convexities gives a bay nearly 1 inch 

 in depth. Traced vertically, there is very little concavity on 

 the upper part of the surface, except on the posterior third. 

 Taken from the glenoid margin, the concavity of the dorsal 

 surface is 3 J inches deep at the great hollow between the 

 beams, 2| inches deep at other parts. The greatest depth of 

 these fossse is at about the junction of the lower and middle 

 thirds of the bone. In B. musculus, the characters on the 

 dorsum also are different. Traced antero-posteriorly, there are 

 the convexities of the anterior and posterior beams, between 

 these a wide general concavity, about 1 inch deep, intersected 

 by a vertical ridge at about the middle of the bone, correspond- 

 ing to one of the deepest radiating fossae of the venter. Traced 

 vertically, the upper part of the surface is a little concave on 

 the anterior third, convex on the posterior third. Taken from 

 the glenoid margin, the depth of the concavity of the dorsal 

 surface is, high up on the anterior third, 2} inches, on the rest, 

 about 1^. 



The glenoid cavity is not only longer than in the mature 

 B. musculus, but is broader in proportion to its length, as seen 

 by the measurements given in Table II. The greatest diameter 

 of the articular head of the humerus in Megaptera is 12^ 

 inches, that of the 60|-feet-long B. musculus is 9i- inches. The 

 greater breadth of the glenoid cavity in Megaptera, as regards 

 outline form, is gained on both sides, but the neck and cavity 

 project more to the outer than to the inner side, to the extent 

 that § of the breadth of the cavity lies to the outside of the 

 plane of the bone. This is not the case in B. musculus, in 

 which the projection to the two sides is either equal or greater 

 to the inner than to the outer side. This difference may be 

 in part owing to the presence of a large coracoid in B. musculus, 

 and to the absence of an acromion process in Megaptera, but it 

 is seen further back and is well marked. 



WeigJit of the Scapula. — The greater robustness of the scapula 

 of Megaptera is shown also by the weights given at the foot of 

 Table II. In the 40-feet-long Megaptera it weighed 528 oz., 

 against 255 oz. in the 50-feet-long B. muscvilus, and against 480^ 

 in the 60 J -feet-long B. musculus. The difference between these 

 two latter is also strikinof. The risfht is heavier than the left 



