EErORT ON THE CETACEA. 25 



anterior four caudals, and had the same shape and direction as in the lumbar vertebrae ; 

 they rapidly diminished in size in the fifth and sixth, and in the seventh were reduced 

 to a foint ridge projecting from the anterior half of the side of the body. Metapophyses, 

 which were non-articular, projected forwards from the anterior edge of the laminae of the 

 anterior seven vertebrae, and a shorter pair of processes projected backwards from the pos- 

 terior edge of the laminae of the anterior four vertebree. The posterior eight caudals were 

 merely the bodies of vertebrae. The inferior surface of the body of each of the anterior 

 fifteen caudal vertebrae was grooved antero-posteriorly, and on this surface in the anterior 

 nine vertebrae were articular facets for eight chevron bones. Only five of these bones 

 were present in this skeleton, viz., the larger and most anterior ; it is not unlikely that 

 the more posterior chevi-ons had not been ossified. 



In von Haast's specimen, as in this, the spinous processes disappeared behind the tenth, 

 and the transverse processes behind the seventh caudal vertebra ; but there were nine instead 

 of eight chevron bones. In both Mesoplodon grayi and Mesojdodon australis, again, Pro- 

 fessor Flower found that the neural arch and spine were present on the eleventh caudal, 

 and that the last trace of the transverse process did not disappear until the ninth caudal. 



The Ribs. — There were nine pair of ribs, corresponding in number to the dorsal 

 vertebra. The first was the broadest and shortest, from which they increased in length, 

 but diminished in breadth, to the fourth, when they again diminished in length to the 

 ninth. The anterior seven each articulated both with a vertebral body and with a 

 transverse process. From the second to the seventh inclusive, each rib possessed a dis- 

 tinct head and tubercle separated by an intermediate neck ; but the first had an elon- 

 gated articular surface at its vertebral end without any definite demarcation into head and 

 tubercle. Each of these ribs was jointed by its head to the body of the vertebra in front 

 of that to the transverse process of which it was articulated by its tubercle, but the head 

 of the seventh rib was articulated with the bodies of botli the sixth and seventh dorsal 

 vertebrae, whilst its tubercle articulated with the transverse process of the seventh dorsal. 

 The eighth and ninth ribs had each only a single articiilar surface at its vertebral end, 

 which was jointed with the transverse process projecting from the side of the body of 

 the corresponding dorsal vertebra. The greatest breadth of the first rib was 2g inches, 

 its length along its posterior border was 11 5- inches. The greatest breadth of the fourth 

 rib was in the region of the tubercle, viz., If ths of an inch, and its length along the 

 posterior border was 2 feet. The length of the last rib cannot be given, as it was broken. 



In von Haast's specimen, where ten ribs were on each side, the eighth, ninth, and 

 tenth had each only a single articular surface at its vertebral end for articulation with 

 its corresponding vertebra. In Mesoplodon grayi, also with ten pairs of ribs, only the 

 ninth and tenth had a single articular surface at their vertebral ends for articulatioji 

 respectively, with the transverse processes from the side of the bodies of the ninth and 

 tenth vertebrae, whilst the eighth rib was attached to the articular surfaces on the cou- 



(ZOOL. CHALL. EXP. PART IV. 1880.) D 4 



