13 
1913-14.] The Auditory Organ in the Cetacea. 
Megaptera* gave 4 inches in the fore part of the carcase and 3 inches 
further back as the thickness of the blubber, but the length of the wax 
club in the South Shetland Megaptera indicated a greater thickness on 
the side of its head. In the Longniddry B. sibbaldi which I dissected in 
1869-70 f the blubber on the top of the beak and cranium was 8 to 15 
inches thick, whilst in front of the dorsal fin it was 12 to 16 inches, and 
behind that fin 14 to 21 inches. 
Tympano-petrous Bones. 
The collection contained the following specimens : — 
Megaptera longimana. — (a) Right and left tympano-petrous bones of the 
Humpbacked Whale, from a specimen captured in 1913 near Bryde Island, 
Graham’s Land; the tympanies were 109 and 113 mm. (4J and 4J inches) 
respectively in length. ( b ) Left tympano-petrous tympanic, 108 mm. long, 
(c) Right and left tympanies, 106 mm. long, (d) Right tympanic, 107 
mm. long. 
Balcenoptera sibbaldi. — (a) Three pairs of tympano-petrous bones of 
the Blue Whale from South Shetland, captured 1912, and (b) a single left 
tympanic. The tympanies as a rule varied in length from 121 to 129 mm., 
but one pair measured exceptionally 146 and 148 mm. (about 5f inches). 
Balcenoptera musculus . — A pair of tympano-petrous bones from a 
whale captured at Admiralty Bay, South Shetland, in November 1912, is 
labelled B.W., i.e. Blue Whale. The examination of these specimens 
satisfied me that the tympanic differed from that bone in B. sibbaldi in 
several particulars, as follows : It possessed a deep groove on the outer 
surface parallel and close to the posterior border, which gave to that border 
a more definite character than was the case in B. sibbaldi. On the other 
hand, it did not possess the long broad groove parallel to and bounding 
the outer side of the lower border, which gave rise in sibbaldi to a very 
prominent keel; the Eustachian end of the tympanic cleft was also less 
scooped out than in sibbaldi. The tympanic was 125 mm. long, 89 high, 
and 77 in greatest breadth. In one of the pair the opisthotic process of 
the petrous was entire, 435 mm. long by 135 mm. in greatest breadth, 
almost identical in its dimensions with those of a large B. sibbaldi. 
Differing from Sibbald’s Whale in several particulars, the tympanies 
more closely corresponded in their characters with B. musculus, so that I 
am disposed to regard this pair of specimens as from that species. 
* Anatomy of the Humpbacked Whale, Edinburgh, 1889. 
t Account of the great Finner Whale, stranded at Longniddry, Trans. Boy. Soc. 
Edin. } vol. xxvi., 1870. 
