CATALOGUE OF THE GET ACE A. 285 
■with the excejstion of those portions of the former which form the deeply -notched lateral walls of 
the posterior nares, and which are continuous with the very broad lateral expansions of the basi- 
occipital. The occipital condyles are nearly an inch apart at their closest approximation below; 
the foramen magnum is large, rounded below, and angular, rather than notched, above. There is 
a sharp vertical lamina on the inner side of the supra- occipital, extending forward in the median 
line, nearly an inch from the inner surface of the supra- occipital, and terminating below about 
half an inch above the foramen in a small triangular tentorium, from which slight laterally 
extending ridges indicate the boundary of the cerebellar fossa. 
The superior aspect of the cranium presents no very distinctive features. Compared with 
Clymenia microps, Gray, as figured in the Zoology of the Erebus and Terror, pi. 25 (also, in Synopsis 
of Whales and Dolphins, 4to., Gray, 1868, pi. 25), the following differences are noted: The pre- 
maxillae are narrower, more elevated above the maxillae ; the nasal triangle extends half an inch 
beyond the posterior end of the tooth line instead of falling about as far behind it, and is much 
more acute in front in D. Bairdii. The posterior angle of the supra -orbital process in D. Bairdii 
is much less prominent, when viewed from above, than in microps, and the extension of the max- 
illaries over the jugals is less elevated, being evenly rounded off at the sides and in front. The 
supra -occipital is pressed in above the condyles, and the superior portion of it is more roundly 
convex than in microps. The proportion of the beak to the brain -case is greater than in Clymenia 
slenorhynchus, Gray, and the beak is wider, both at the notches and anteriorly. The laterally 
channeled palate would in any case distinguish it from the species of Clymenia and Steno, to which 
it bears a superficial resemblance. In the anterior third of the beak, the premaxillae evenly slope 
off toward the maxillae in the same plane, and are separated by the mesethmoid cartilage. Behind 
this, however, the premaxillae are solidly united, and much more elevated above the maxillae, 
forming a ridge with nearly parallel and vertical sides, rounded off above, and attaining a maximum 
height above the maxillae of 0.43 of an inch. The nasal triangle is evenly excavated, divided by 
an open suture terminating in a notch above the narial septum. The mesethmoid plate is provided 
with a submedian ridge, and terminates above in three points. The nasals are knob -like and 
rounded transverse, forming the vertex of the skull. 
Cervical Vertebra. — These are coossified into three groups, as hereafter mentioned; but it is 
probable that individuals vary in this respect to some extent. The first mass has a total diameter, 
from point to point of the transverse processes, of 5.35 inches; and from the middle lower anterior 
edge of the atlas to the bifurcation of the spinous process of 3.65 inches. The neural arch is 1.10 
inch high and 1.53 inch wide; the extreme width across the condylar facets is 3.3 inches. The 
centrum of the third cervical is 1.3 inch wide by 1.0 inch high. The neural arch (incomplete at 
the top), 0.92 inch high by 1.0 inch wide; the extreme width from point to point of the vertebra 
is 1.65 inch. The fifth cervical has a total width between the points of the lower transverse 
processes of 1.57 inch. The height of the centrum is 1.1 inch; of the neural arch, 0.8 inch; the 
width of the centrum is 1.15 inch; of the neural arch, 0.89 inch. The length of that part of the 
vertebral column composed of third, fourth, fifth, sixth, and seventh cervicals is 1.2 inch, and that 
part composed of the atlas and axis, 1.0 inch more. The neural spine of the seventh cervical is 
0.8 inch long, and the width from point to point of the transverse processes, 3.65 inches; of the 
second thoracic, the spine is 1.6 inch, and the width 3.55 inches. 
The first mass consists of the atlas and axis solidly coossified both by their spines and bodies, 
so that the only vestige of separation is an ovate and somewhat oblique opening between the 
pedicels of the arches. The inferior portion of the atlas is much produced forward, giving an 
oblique appearance to the whole bone, which is of an approximately triangular shape. Its arch is 
transversely ovate, with a broad triangular space between the condylar facets. The first spinal 
nerve enters by a shallow groove over the latter. The transverse processes appertaining to the 
atlas are rather long and obliquely flattened above and below, with a slight knob, indicating a 
superior transverse process, just above them. These two processes are separated by a narrow 
groove from two nodular projections which indicate the corresponding parts in the axis. A slight 
ridge exists on the inferior surface of the centrum. The neural spine is very broad, stout, and 
