40 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76 



intervening between the formation of the chondrocranium and the 

 essentially final structure of the skull. Early conditions in two of 

 the mysticetes were figured many years ago by Eschricht in his well- 

 known accounts of Balccna inysficetus and Balcenoptera acutorostrata ; 

 recent contributions to the subject have been made by Schulte (Mem. 

 Am. Mus. Nat. Hist., n. s., Vol. I, pis. 54-56, 1916; BalcEnoptera 

 borcalis) and Ridewood (Phil. Trans. Roy. Soc. London, ser, B, 

 Vol. 211, pp. 209-272, May 8, 1922; Megaptera and Balcenoptera). 

 In the absence of more complete information I shall not attempt 

 any discussion of the evidence furnished by the structure found 

 in embryos. 



REMARKS ON THE CLASSIFICATION HERE ADOPTED 



The classification of the cetacea to which the present study of 

 telescoping has led is as follows : 



Order Cetacea. 



Suborder Arch^oceti ( = Series I). 

 Family Protocetidce (Protocetus). 



Family Doriidonfidcc ("Zeuglodon" with short vertebrse). 

 Family Basilosauridcr (Basilosauriis). 

 Suborder Mysticeti (=: Series II). 



Family Balcenid<B {Balcena, Eubalmia). 



Family Neobalcenidce {Neobalcena). 



Family Cetothcriidcc (Cetotheriiim and allied extinct genera). 



Family Rhachianectidce (Rhachianectes) . 



Family BaJcvnoptcridcc. 



Subfamily Mcgaptcrina {Megaptera) . 

 Subfamily Balccnopterince {Balcenoptera, Sibbaldus). 

 Suborder Odontoceti (=: Series III). 



Family Agorophnd<2 (Agorophitis, Archceodelphis, Xenorophus ; per- 

 haps Patriocctus) . 

 Family PhyseteridcE (Physetcr; position of extinct related genera un- 

 certain). 

 Family Kogiidce (Kogia; position of extinct related genera uncertain). 

 Family Squalodontidce (Squalodon; Prosqualodon ?) . 

 Family Iniidce (Inia, Lipotes, and several extinct South American 



genera). 

 Family Delphinidce. 



Subfamily Dclphinince (The typical dolphins). 

 Subfamily Eurhinodelphinince (Enrhinodelphis if correctly de- 

 scribed). 

 Subfamily Sienodelphinina (Stenodclphis, Palccopontoporia; per- 

 haps Argyrocetus). 

 Subfamily Delphinapterhice (Delphinapterus only). 

 Subfamily Monodonthicc (Monodon only). 

 Family Ziphiidce (The beaked whales). 

 Family Plafanistid<s (Platantsfa only). 



