Bibliographical Notices. 195 
longitudinal grooves, about an inch deep, which extend forward to 
near the extremity of the lower jaw. ‘The tail-fin is 4 fect long in 
the middle, and each lateral half is 8 feet long. The dorsal fin is 
only 15 feet from the extremity of the tail, and is placed above the 
anal region ; it is 23 feet long. The body is dark slate-grey, with 
the back nearly black. The second specimen was 60 feet long, and 
had about one hundred furrows on the underside. The sexual 
differences are indicated; and it would seem that, notwithstanding 
the larger size of this individual, the anal aperture is only 15 feet 
from the extremity of the tail. The lobes of the tail are smaller, 
and each is only 63 feet wide; the back fin also is smaller. The 
male specimen is more slender and of a darker colour, and has rela- 
tively smaller pectoral fins. The baleen extends along the mouth 
for about 6 feet; the plates are triangular, and where longest have a 
length of 2feet. They diminish in length to a few inches, and form 
mere pencil-like tufts. 
In this second specimen the entire length of the skull is only 10 feet 
8 inches, and is only a little longer, but relatively wider, than that 
of Balenoptera patachonica. 
The outer border of the maxillary bone is remarkably convex ; the 
lateral parts of the occipital bone do not diverge backward so much 
as in the other species ; the nasal bones extend back to the line of 
the orbit ; the premaxillary bones have a remarkable process incli- 
ning inward, where the frontal branch of the maxillary diverges—a 
condition somewhat similar to that seen in the Balenoptera Sibbaldii. 
Thus the distinction of this species from those which it most resem- 
bles is set forth. Similarly the vertebral column is somewhat 
stronger than in the foregoing species. There are seven cervical, 
fifteen dorsal, sixteen lumbar, twenty-six caudal vertebre. The 
detailed descriptions and measurements assist the figures in illustra~ 
ting the characters of this part of the skeleton; and the author 
follows the same general plan previously adopted in his descriptions, 
The sternum was lost in maceration. The fore limb is almost en- 
tirely unknown, though the author gives a beautiful drawing of its 
osteology on the basis, as he states, of analogy with its northern 
representative. 
Megaptera Burmeisteri is still only known from the skeleton, 
50 feet long, which was found overgrown with willows on an island 
in the delta of the Parana, where it lay partly buried; and but few 
additions have been made to the original materials, though among 
these are the tympanic and petrosal bones. 
Balena australis occurs off the South-American coast; but no 
specimen has hitherto been captured in the Argentine waters. 
Finally, in a brief conclusion, the author justifies his mode of 
dealing with the material. 
The descriptions are excellent throughout, and relieved by a 
recital of incidents in the history of the specimens which are not 
without humour. The illustrations leave nothing to be desired ; and 
the work will take a place among important ‘monographs of the 
Cetacea. 
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