EASTMAN: sharks' TEETH AND CETACEAN BuNES. 87 



preserved in natural association with the skull, a conspicuous example 

 being the type of Lophocetvs calvertensis (Harlan). Thus it appears 

 that the subject is eminently worthy of further cultivation, and one is 

 gratified to note that within the last few years signs of renewed interest 

 have become manifest in the writings of several continental palaeontol- 

 ogists, notably Abel,^ Dal Piaz,"-^ and Flot.^ 



Any comparative study of the bones related to the organ of hearing 

 in Cetaceans, whether fossil or recent, must take careful account of 

 certain minutiae, the nature of which may best be explained by describ- 

 ing these parts in a typical example, such as is furnished by the recent 

 Delphinapterus leucas. The description here offered will be found to 

 correspond closely with the accounts that have recently been given of 

 the auditory organs of the Porpoise by Beauregard,* Denker, and Boen- 

 ninghaus, whose papers contain a mass of valuable information, both 

 anatomical and physiological, besides abundant references to the litera- 

 ture. We have also adopted the same designations of parts as employed 

 by these authors, and have arranged and lettered the accompanying text 

 figures so as to correspond with the series of Plwcaena communis given 

 by the last mentioned. The aspects selected for illustration are ob- 

 tained by rotating the specimen upon its axis through successive quad- 

 rants, and then turning it end for end. There are thus shown in order 

 the external, superior, internal, and inferior surfaces, and finally the 

 two end-views. 



General Characters of Cetacean Ear-Bones as Illustrated by 



Delphinapterus. 



(Text-figures A-F.) 



In the genus under consideration, as in Delphinoids generally with 

 the possible exception of Platanista, the united tympanic and periotic 



1 Abel, 0., Untersuchungen iiber die fossilen Platanistiden des Wiener Beckens. 

 Denkschr. k. Akad. Wissensch. (1000), 68, p. 8.39-874. Les dauphins longi- 

 rostres du Bolde'rien des environs d'Anvers. Mem. Mus. Eoy. d'Hist. Nat. Belg. 

 Annee 1901, p. 1-9-5. Part II., ibid., 1902. Eine Stammtype der Delphiniden aus 

 dem Miocan der Halbinsel Taman. Jahrb. k k. geol. Reiehsanst. (1905), 55, p. 375. 

 Les Odontocctes du Bolde'rien d'Anvers. Me'm. Mus. Roy. d'Hist. Nat. Belg. 

 Anne'e 1905, p. 1-155. 



2 Dal Piaz, G., Sugli avanzi di Cyrtodelphis sulcatus dell' arenaria di Belluno. 

 Palaeont. Ital. (1903), 9, p. 187-219. Part II., ibid. (1905), 11, p. 253-280. 



3 riot, L., Note sur les Cetace's fossiles de I'Aquitaine. Bull. Soc. Ge'ol. 

 France (1896), 24, p. 270-282. 



* Beauregard, H., Recherches sur I'appareil auditif cliez les mammifures. 



