430 PROF. W. H. FLOWER ON THE GENUS MESOPLODON. 
Berardius. They are all completely united above, except the fifth of the young I. grayi. 
In the sixth, in both specimens, the spine is so well developed as to equal in height the 
spinal canal over which it is placed. In the seventh, in VW. australis, it, is considerably 
higher than in WV. grayi, and also much stouter at the base. It is a question, however, 
how much the difference between the two may be due to age. The seventh in both 
has a large articular surface on the posterior edge of the side of the body for arti- 
culation with the head of the first rib. At the lower end of this surface is a small 
tubercle representing the inferior transverse process of the preceding vertebra. 
Dimensions of the Cervical Vertebre. 






j 7 
M. australis. | M. grayi. 
inches. | millim. || inches. | millim. 
Antero-posterior length of the bodies of the seven vertebra in con- | 
caati (interior suriace) mt Site eae She wtvilersteertac tare Pie eteve ebaene Bol} 130 || 4:9 124 
Length of body of united first and second .............+...00- 1:9 48 || 1:7 43 | 
ene tihvols Dod ysoieeyOmuly one cternnra:stsrsiare crnawesaremensisy a caventer star oe “9 23 6 15 
| Height from top of spine to lower edge of body of atlas .......... Sel | 130M 4:65 | LA 
| oy a on third vertebra ..| 4:1 104 || 35 89 | 
| es - a sixth vertebra ..| 5:5 140 || 50 127 |} 
a * 3 seventh vertebra.) 7-1 180 || 56 142° | 
Breadth between outer borders of articular surfaces of atlas ....... 3-7 | 94 || 39 99 | 
Breadth between ends of transverse processes of atlas............ 56 | 142 || 55 | 140 
| | 




It will be seen from the above that the only measurement in which MW. grayi exceeds 
M. australis is the width of the surfaces for articulation with the occipital condyles. 
This, taken in conjunction with the immaturity of the specimen, is a tolerably sure 
indication that it would, if adult, attain a larger size than the latter. 
The thoracic vertebra of both skeletons present all the characteristic features of the 
group, the most remarkable of which is the sudden transition of the articulation of the 
ribs from the upper to the lower processes, by which the Physeteride are distinguished 
from the Delphinide. The principal difference between the two is that in WZ. australis 
there are but nine with nine pairs of ribs (as in Hyperoodon), whereas in M. grayi there 
are ten, as in all the other recorded examples of JJesoplodon’. 
In the erect high spines of the thoracic vertebrae Mesoplodon resembles both Ziphius 
and Hyperoodon, and differs in a marked manner from Berardius’. 
Tt should be mentioned that, according to Hector’s original description (Trans. N.Z. Inst. vol. vii. p. 262), 
the skeleton of M. australis had ten pairs of ribs; but the number now present with it is that which I have 
stated above, and the vertebra which I have reckoned as the first lumbar bears no trace of an articulation for 
arib at the end of the transverse processes. Moreover a close comparison shows that the rib which is wanting 
would not correspond to the last of J. grayi or the other ten-ribbed species, but rather to one from the middle 
of the series; and yet there is no indication of the accidental loss of both vertebra and pair of ribs, which must 
have been the case if Dr. Hector’s enumeration was correct. 
* See Trans. Zool. Soe. vol. vili. p. 226. 
