14 
Proceedings of the .Royal Society of Edinburgh. [Sess. 
This series of tympanies are of importance in showing that the 
Balsenopteridse, Megaptera longimana, Balcenoptera sibbaldi, and B. 
musculus, which frequent the North Atlantic and are; captured in Scottish 
waters, are also denizens of the South Atlantic. The University Museum 
also contains a pair of tympanic bones from Balcenoptera borealis, 
Rudolphi’s whale, the Sye Whale, from the South Atlantic,* captured in 
1911, which is also a Scottish species. 
Many naturalists have described with more or less detail the tympano- 
petrous bones in the whalebone and toothed whales. I have also figured 
in my descriptive Catalogue f the characters of the tympanies in a large 
number of species. The additions to the collection through the recent gift 
of Mr Coughtrey have enabled me to study more completely the relations 
of the tympanic and petrous bones to each other, to the chain of tympanic 
ossicles, and the approximate arrangement of the membrana tympani and 
the external auditory meatus. Carte and Macalister had previously given a 
careful description of the tympano-petrous in Balcenoptera rostrata, and 
Struthers had recorded their characters in Megaptera longimana, but the 
dissections of D. G. Lillie of the region in Balcenoptera musculus are much 
more complete, as he had the advantage of studying the bones along with 
the associated soft parts. The University collection contains specimens of 
these bones in both the whalebone and toothed whales ; they corresponded 
with each other in general characters, though with modifications in detail, 
which expressed specific and generic differences. In no specimen, however, 
had the external meatus, the tympanic membrane, and the Eustachian tube 
been preserved. 
The following description is based on the characters of the tympano- 
petrous bones in Balcenoptera sibbaldi, \ though with specific modifications it 
applies generally to the baleen whales. The tympanic bone was keeled on 
its inferior surface. Its outer surface was convex and marked by an 
oblique, strong, relatively wide groove-like depression which divided it into 
an anterior and a posterior part, the latter of which was the larger. The 
upper border of this surface was sinuous and was connected by a broad 
posterior pedicle to the under-border of the long, flattened, winglike opis- 
thotic process of the petrous. The anterior surface of the posterior pedicle 
was hollowed, smooth, directed towards the tympanic cavity and the meatus, 
* Catalogue, p. 58 ( G . Bpt., 5). I described a Scottish specimen in Journ. Anat. and 
Phys ., April, 1882. 
+ The Marine Mammals in the Anatomical Museum of the University of Edinburgh , 
London, 1912 ; also “ The Right Whale of the North Atlantic ( Balcena biscayensis )” in Trans. 
Boy. Soc. Edin ., vol. xlviii. part 4, 1913. 
I The University Museum now contains eighteen tympanic bones of Sibbald’s Whale. 
