192 Bibliographical Notices. 
The skull is compared by the author with that figured by Esch- 
richt as Balenoptera rostrata, from which it differs in carrying on to 
the mature condition the form which distinguishes the northern 
whale in the young state. The Argentine whale has the snout rela- 
tively shorter and more pointed. The expansion between the pre- 
maxillary bones is posterior in position, and oval; the nasal bones 
are small and narrow; and the frontal bone reaches further forward 
and is narrower in the orbital region than in the northern form. 
The occipital bone has the parabolic contour of the young Bale- 
noptera rostrata, and covers the parietal and reaches the nasal, 
so as nearly to overlap the frontal bones. The fork of the maxil- 
lary is short. The palatine bone is short, and truncated rather than 
rounded in front. The jugal process of the squamosal bone does not 
extend so far outward as in the European species ; and the jugal bone 
is slender and more curved in front. The vomer is relatively longer, 
and is partly cleft in front. These differences, which are regarded 
as specific, are accompanied by other differences in the vertebral 
column, though the number of vertebre is the same. There are 
7 cervical, 11 dorsal, 12 lumbar, and 18-20 caudal vertebrae. The 
first, second, fourth, and fifth cervicals are figured separately ; and 
the author points out the many small differences which he regards 
as characterizing the South-Atlantic type, at the same time con- 
fessing that he no longer attaches so much importance to the lateral 
blending of the transverse processes into rings, as he did when the 
species was first instituted. In the dorsal region the spinous process 
increases in height from the first, in which it is 5 centim. long, to 
38 centim. in the last dorsal. The height of the process increases 
to the middle of the lumbar region, and then declines, so that the 
process altogether disappears at the tenth caudal. The modifica- 
tions of the vertebra in the dorsal region are represented by drawings 
of the vertebral column and of the first and last dorsals, from which 
it is seen that the neural canal, which is at first triangular and 
has a slender arch, becomes ultimately vertically oval as the arch 
increases in strength, and the transverse processes, which were at 
first directed forward, come to be turned backward. The caudal re- 
gion is characterized by the third to the tenth vertebra having vertical 
perforations, which in the earlier vertebrae pass through the bases 
of the transverse processes, and in the later vertebre through the 
centrum. ‘There are twelve subvertebral bones in the caudal region. 
The tail-fin probably extended over six vertebra. The ribs vary in 
the position of the tubercle and in their length and curvature. The 
first is 86 centim. long; the seventh is 146 centim. round the 
curve, while the tenth and eleventh are 92 centim. in the same 
measurement. The sternum is very remarkable in having the 
anterior limb of the cross subdivided into two; it is 44 centim. 
long and has the usual facets for the first rib on the middle of the 
posterior process. The scapula is chiefly remarkable for the sharp- 
pointed form of the acromion and coracoid processes. The fore limb 
is somewhat slender, with the humerus 28 centim. long and the 
ulna and radius 56 centim. long. Both these bones are curved 
