234 DR. J. E. GRAY ON BRITISH CETACEA. [May 24, 
The tympanic bone is small, scroll-like, oblong, anchylosed to a 
somewhat similar-shaped tegmen tympani and pars mastoidea (see 
Owen, Hist. Brit. Fossil Mam., fig. of natural size (not half the na- 
tural size, as marked on the plate). 
When the young Cachalot has attained the length of 34 feet, its 
teeth are perfectly formed, though not visible until it exceeds 28 
(Bennett, P. Z. S. 1836). 
Mr. Bennett found eight rudimentary teeth on each side of the 
upper jaw in two instances, which, ‘ though not visible externally in 
the young Cachalot, may be seen upon the removal of the soft parts 
from the interior of the jaw” (Proc. Zool. Soc. 1836). 
Professor Huxley has figured the skull of a fcetal specimen that is 
in the Museum of the College of Surgeons, at fig. 118, on page 275 
of his ‘ Elem. Comp. Anat.’ 1864. 
In the fceetal skull the right preemaxilla is much larger than the 
left, extending far back upon the right frontal, while the left does 
not reach the left frontal; the left nostril, on the other hand, is 
much more spacious than the right (see Huxley, Elem. Comp. Anat. 
276. f. 1104). 
** Head depressed, rounded in front ; nostrils in the forehead ; 
dorsal fin falcate. 
2. PHysreTEerR. 
Head very large, one-third of the entire length of the animal, 
rounded, convex above. Teeth conical, compressed. Skull elongate. 
Physeter, sp., Linn. 8. N. ; Illiger, Prodr. 143; Gray, Z. E. & T.; 
Cat. Cet. 53. 
Tursio, Fleming, Phil. Zool. 211. 
Cetus, Oken. 
Cuvier (Oss. Foss. v. 328, 338) erroneously regards Sibbald’s ac- 
count as a bad description of a Sperm Whale. This error is impor- 
tant, as it vitiates many of his subsequent observations. 
PHyYSETER TURSIO. The Blackfish. 
Physeter tursio, Gray, Cat. Cetac. 56. 
1. Balena macrocephala que tertiam, &c., Sibbald, Bal. t. 1. 
f. A, B, C. 
Balena major, Se., Raii Pisces, 15. 
Physeter microps, Artedi, Syst.; Turton, B. F. 17; Fleming B. 
A. 38; Jenyns, Man. 46. 
Physeter macrocephalus, Cuvier, Oss. Foss. v. 331, 334. 
Tursio microps, Fleming, Phil. Zool. 21. 
2. Balena macrocephala tripinna, &c., Sibbald, Bal. t. 2. f. 1, 2, 
4, 5, teeth; Raii Pisces, 16. 
Physeter tursio, Artedi, Syst.; Linn. S. N. i. 107. 
Physeter ?, Schlegel, Dieren, 96. t. 19; Turton, B. F. 17; 
Fleming, B. A. 38; Jenyns, Man. 45; Bell, Brit. Quad. 512. 
Delphinus globiceps or D. grampus?, Cuvier, Oss. Foss. v. 331. 
fab. North Sea, Scotland (Sibbald, Barclay). 
