ART. 15 ANATOMY OF THE EARED AND EARLESS SEALS — HOWELL 21 



plate, with the suggestion of two processes upon its caudal and one 

 upon the cranial termination. In the fourth the cranial has disap- 

 peared, or rather is undifferentiated from the remainder of the plate, 

 but the two caudad are more distinct, the superior being directed 

 farther dorsad. In the fifth this has become a distinct anapophysis, 

 separate from the papapophysial plate. In the sixth this condition 

 is much more pronounced and the robust caudal termination of the 

 parapophysial plate exhibits a separate center of ossification. In 

 the seventh, partly because this is the first vertebra lacking a lateral 

 vertebral canal, the inferior process, which is a true process and not 

 a plate as in those more craniad, is situated more dorsad, where it 

 should be considered as a diapophysis. It also has an anapophysis 

 like the sixth. Metapophyses are lacking in all. Conditions are 

 somewhat similar in the Phoca with the exception that there is little 

 tendency for the parapophyses to be platelike, save the sixth as usual 

 and in the seventh the anapophysis and diapophysis have virtually 

 fused. In the Zalophus there is a gradual increase in the height of 

 the neural spines from the third to the seventh, the latter being 

 53 mm. in height above the neural canal, while in the Phoca there are 

 really no spines upon the last five cervicals, that of the seventh 

 measuring but 12 mm. in height. 



Thoracic vertebrae. — The thoracic series of vertebrae normally 

 constitutes 15 in all pinnipeds except Odohenus, in which there are 

 14, for out of 47 individuals of 14 species and genera, of both orders. 

 Thomson (1909) encountered but 1 with 14 thoracics; so Flower 

 (1876) was mistaken in his statement that Phoca has but 14. In 

 Zalophus the series constitutes 67 per cent, and in the Phoca 57 per 

 cent of the body length (46 in a cat). Hypapophyses are distinctly 

 present in the first four and the fifteenth, the latter especially pro- 

 nounced in the otariid. The neural spines gradually decrease in 

 caudal sequence from the first, which is of about the same height as 

 in the seventh cervical, and they exhibit no pronounced anticline or 

 change in direction, as they do in most carnivores, nor any abrupt 

 change in character, although there is a gradual broadening of the 

 spines. As far caudad as the eleventh vertebra in Zalophus the 

 articular surfaces of the zygapophyses are horizontal. Those be- 

 tween the eleventh and twelfth and thereafter (including the lum- 

 bars) become progressively more vertical, but the significant feature 

 in this animal is that in all posterior to the first few the two post- 

 zygapophyses of each vertebra are exceedingly close together, theo- 

 retically allowing of great freedom of movement. In the posterior 

 thorax, however, there is such interlocking of the zygapophyses that 

 a very concave outline of the dorsum can not be assumed, but the 

 convexity, especially in the lumbar region, is onl}^ limited in degree 

 by the elasticity of the intervertebral disks. - 



