530 CETACEA. 



flattened than in Inia, and it is marked by a pointed longitudinal ridge or spine, 

 and it is rather deeply notched anteriorly at its base, for the suboccipital nerve and 

 vertebral artery ; and above the facet for the occipital condyle, a sharp process pro- 

 jects upwards and inwards from the inferior to the superior angle of the notch to 

 such an extent that it is possible the notch in some individuals may become convert- 

 ed into a foramen. The inferior arch is very broad and strong, having a well- 

 developed hypapophysial process for the support of the odontoid and a large concave 

 facet on its upper surface for its reception. The posterior zygapophyses are unsym- 

 metrical, the left being considerably larger than the right, and projecting inward 

 beyond the inner wall of the neural canal, which it also renders unsymmetrical . 

 The base of the left facet and the right half of the odontoid facet are slightly raised 

 above the level of the corresponding parts on the left side. The upper surface of 

 the posterior facets are deeply grooved. The neural canal is broad above and narrow 

 below. 



The axis is distinguished by its very largely developed superior transverse pro- 

 cess directed backwards and outwards. The odontoid is well developed and has a 

 large articular facet on its under surface, and it is slightly twisted to the left. 

 The neural canal is broader than high and arched with a broad flattened floor. The 

 arch is broad, antero-posteriorly high, directed slightly backwards, and the spinous 

 process is traversed by a well-marked ridge which terminates anteriorly in a free 

 process, the apex of the spinous process being more or less bifid. The body of the 

 axis is concave below and terminates in two posteriorly divergent, strong hypapo- 

 physes. The anterior zygapophyses, the upper extremities of which are on a level 

 with the inferior border of the posterior zygapophyses, their inferior margins being 

 on a line with the under surface of the odontoid, partake of the same want of 

 symmetry that distinguishes the posterior surfaces of the atlas. Their surfaces are 

 not continuous with the articular surface of the odontoid, so that the lateral 

 movement of the head cannot be very great. The articular surface of the 

 centrum is transversely oval, and the epiphysial surface markedly concave in the 

 middle. 



The third cervical has a very short centrum, a little broader than high. The 

 neural canal is triangular, considerably broader than high, and with very narrow 

 laminae, directed slightly backwards, and presenting some very small processes at 

 their point of union, but no further trace of a spinous process. The transverse 

 process, occasionally perforated by a vascular foramen, has an antero-posteriorly thin, 

 but deep base, which embraces two-thirds of the side of the centrum, sending for- 

 wards a small process from its inferior basal margin. Its upper border, below the 

 zygapophyses, has a deep intervertebral notch, the inferior outward limit of which 

 is defined by a small sharp process. The process hes immediately anterior and close 

 to the transverse process of the axis, but has the superior transverse process of the 

 fourth vertebra behind and above it. The zygapophyses are on the same level at 

 the outer end of the laminae, and the two of the right side are of about one size, 

 but the posterior zygapophysis of the left side is very small. 



