20 PEOCEEDINGS OF THE NATIONAL MUSEUM voi.. 7;i 



of Zalophus comprises 44 vertebrae and of the Phoca 45,- which 

 seems to be a greater number than is possessed by most pinnipeds 

 because of the numerous caudals. It is, of course, almost impossible 

 to decide whether there has been any actual lengthening of the pin- 

 niped vertebral column in relation to general body mass. There 

 seems to be a tendency toward lengthening of the thorax in the 

 Otariidae at least, but the lumbar length of fissipeds is entirely too 

 variable for one to make comparisons in this series. Outstanding 

 details of the vertebral column are the slight development of the 

 spinal processes in phocids, highest in the extreme ant-erior thoracic 

 series of otariids; the thickness and evidently great elasticity of the 

 intervertebral disks, especially in the cervical and lumbar region of 

 otariids ; and the osteological provision, also especially in the otariids, 

 to allow for extreme mobility of the individual vertebrae, the pre- 

 and post-zj^gapophyses being reduced and also all bony details that 

 might collide with an adjoining vertebra during contortive move- 

 ments. The nomenclature used for the vertebral processes is that 

 most often employed (see Howell, 1926), save in the case of the 

 diapophyses. It is perhaps wise to employ this term only for such 

 inferior processes when they arise from the neural arches, terming 

 them parapophyses when they arise from the centra. I do not pass 

 upon the propriety of this course but follow it for the reason that it 

 conforms to embryological evidence. The investigation of the varia- 

 tion in the back musculature from a comparative standpoint is one 

 that takes a high order of specialization on the part of the investi- 

 gator, and until some qualified person shall have done this the 

 homolgy of the vertebral processes must be considered as not 

 unassailably established. 



Cervical vertebrae. — The cervical series numbers seven as usual. 

 In the Zalojyhus it measures 24 and in the Phoca 26 per cent of the 

 body length (27 in a cat). That this difference is so slight is rather 

 surprising, for with its apparently longer body, the otariid appears 

 to have a much longer neck; but the difference is increased during 

 life by the considerably greater thickness in the former of the inter- 

 vertebral disks. Although the cranial articular facets in ZalophiLS 

 are relatively much narrower than in the Phoca, to allow for greater 

 freedom of movement in the former, the transverse processes are 

 somewhat broader and directed more s^entrad, a condition attribut- 

 able in part to the greater complexity in this otariid of the longus 

 colli. To this stimulus is also partly due the differences shown by 

 the more ventral of the vertebral processes. The axis in both ani- 

 mals has a very small process which seems to be an anapophysis. In 

 the Zaloyhus the third cervical shows ventrad only the parapoi^hysial 



2 See p. 22. 



