PROF. W. H. FLOWER ON THE GENUS MESOPLODON. 43 
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pairs of ribs‘. In the former the first to the seventh inclusive have distinct articular 
surfaces on the head and the tubercle; the seventh on the left side is transitional; the 
remainder want the neck and head, articulating only by the tubercle to the extremity 
of the transverse process of the vertebra. 
In WM. grayi the first to seventh on both sides have distinct necks, and capitular and 
tubercular articular surfaces; the three others, wanting the head and neck, articulate 
only by the tubercle to the extremity of the transverse process. The general characters 
of the ribs are, of course, more marked in the older specimen ; but otherwise they agree. 
The first is very broad and flat; and in all the angle and a space beyond presents a 
more or less strongly pronounced flattened surface on the outer side, with prominent 
posterior edge. This character, scarcely seen in the first, gradually becomes more 
marked to the last. None of the ribs materially increase in breadth at the lower 
extremity. 
The sternal ribs in both skeletons, as in all Physeteride, are not ossified. 
Pectoral Limb.—The scapula is perfectly delphinoid in form, more even than in 
Berardius, and therefore further removed from Physeter than any other Ziphioid, 
Hyperoodon being the nearest. The only differences between the two specimens are 
such as might arise from want of ossification of the suprascapular cartilage, and of the 
end of the coracoid process in the younger specimen. The humerus, and especially the 
ulna and radius, present the simple elongated narrow form characteristic of the 
Ziphioids, and by which they are easily distinguished from the Delphinide. Allowing 
for difference of age, there is nothing by which the two individuals can be specifically 
distinguished. The same can be said of the bones of the manus, as far as the available 
materials serve for comparison. In MV. grayi both are quite complete; and in WZ. aus- 
tralis one hand is nearly so. 
This segment of the limb closely resembles that of Berardius®, except that the 
singular union of scaphoid and lunar, and of cuneiform and unciform bones, noticed 
in that animal, does not occur. The bones of the first row, the scaphoid, lunar, 
cuneiform, and pisiform, are all distinct. In the second row the trapezoid and 
magnum are united into a single bone, as in the skeleton of MW. didens in the Brussels 
Museum ?*. The first digit has a single slender phalanx; the second has six, the third 
the same number, the last being a minute nodule, scarcely larger than a pin’s head; 
the fourth has three, and the second two phalanges. ‘These are the complete number 
of the adult skeleton. 

‘ Dr. Haast mentions in a letter (dated March 8th, 1876) that one specimen of M. grayi has ten, another 
eleven pairs of ribs. 
* Trans. Zool. Soe. vol. viii. pl. 28. fig. 10. 
* In the specimen at Gothenburg, Malm figures these bones as distinct, Joc. cit. pl. v. fig. 52. 
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