﻿NO. 6 



FOSSIL WHALEBONE WHALES TRUE 



Amphicetus Van Ben. 

 Aulocetus Van Ben. 

 Balanoptera Lacep. 

 Burtinopsis Van Ben. 

 Cetotherium Brandt. 

 x Cetotheriophanes Brandt. 

 Cetotheriopsis Brandt. 

 Cephalotropis Cope. 

 Cetotheriomorphus Brandt. 

 x Eucetotherium Brandt. 

 Herpetocetus Van Ben. 



Heterocetus Van Ben. 

 Isocetus Van Ben. 

 Idiocetus Capellini. 

 Mesocetus Van Ben. 

 Metopocetus Cope. 



Mesoteras Cope. 

 Megaptera Gray. 

 Megapteropsis Van Ben. 

 Plesiocetus Van Ben. 

 1 Plesiocetopsis Brandt. 

 Pachycetus Van Ben. 

 Rhegnopsis Cope. 

 Siphonocetus Cope. 

 Tretulias Cope. 

 £//«« Cope. 



WINGE 



Equals Plesiocetus Van Ben. 



Valid. 



Valid. 



Equals Megaptera Gray. 



Valid. 



Equals Plesiocetus Van Ben. 



Equals Aulocetus Van Ben. 



Equals Plesiocetus Van Ben. 



Doubtful. 



Equals Cetotherium Brandt. 



Valid. 



Equals Plesiocetus Van Ben. 

 Equals Plesiocetus Van Ben. 

 Equals Plesiocetus Van Ben. 

 Equals Plesiocetus Van Ben. 

 Probably equals 



Plesiocetus Van Ben. 

 Doubtful. 

 Valid. 



Equals Megaptera Gray. 

 Valid. 



Equals Plesiocetus Van Ben. 

 Doubtful. 



Probably equals Cetotherium. 

 Probably equals Cetotherium. 

 Doubtful. 

 Doubtful. 



TRUE 



Concurrence. 



Concurrence. 



Concurrence. 



Equals Plesiocetus ? 



Concurrence. 



Concurrence. 



Concurrence. 



Valid ? 



Concurrence. 



Concurrence. 



Probably 



equals Plesiocetus. 

 Concurrence. 

 Concurrence. 

 Concurrence. 

 Concurrence. 

 Valid ? 



Concurrence. 



Concurrence. 



[Not studied.] 



Concurrence. 



Concurrence. 



Concurrence. 



Doubtful. 



Doubtful. 



Concurrence. 



Concurrence. 



The subjoined diagnoses of the genera are, as already mentioned, 

 based only on characters of the skull, as a full comparison of the 

 remainder of the skeleton is not feasible at this time. It is recognized 

 that they are incomplete and subject to revision, but it is thought that 

 they may be of use as a basis for a fuller characterization of the 

 genera. 



Diagnoses of genera of fossil whalebone whales allied to 



Bal^enoptera 

 BAL^NOPTERA Lacepede. 1805 2 

 Orbital plates of frontal on a lower level than vertex, much pro- 

 duced anteriorly. Maxillae produced proximally in a narrow exten- 

 sion at side of nasals. Proximal end of premaxillse narrow, scarcely 



1 Subgenus. 



2 Megaptera cannot be distinguished from Balcenoptera generically by the 

 skull alone. 



