114 BAL^TINOPTERIDJ!, 



II. Dorsal Jin hif/h, erect, compressed, falcate, ahmit thrce-fmirths the 



entire lemjfli from the nose. Pectoral fin nioderate, xvith 4 sltort 

 Jinyers of 4 or G jjhalanges. Vertehrce 55 or G4. Cervical vertehrce 

 not anchylosed. Neural canal ohlong, transverse. Hibs 14 or 15. 

 Physaliua, or Firmer Whales. 



* Vertehrce 60 or 64. First rib single-headed. 



4. Brnedenia. Rostrum of skull narrow, attenuated, with straiglit 



slanting sides. Second cervical vertehra with two short truncated 

 lateral processes. First rib single-headed. 



5. Physalus. Rostrum of skull narrow, attenuated, with straight slant- 



ing sides. Second cervical vertebra with a broad lateral process with 

 a large perforation at the base. First rib singie-headed. Stenium 

 trifoliate, with a long slender hinder process. 



6. CuviERius. Rostrum of skull broad, the outer side curved, especially 



in front. The second cervical vertebra with two short thick lateral 

 processes. First rib single-headed. Sternum oblong ovate, trans- 

 verse, 



** Vertehrce 55. First rib double- headed. 



7. SiBBALDius. Second cervical vertebra with a broad lateral process 



perforated at the base. First and second ribs double-headed. Lower 

 jaw compressed, with distinct coronoid process. Vertehrce 55, 



III. Dorsal Jin high, erect, compressed, about two-thirds of the entire length 



from the nose. Pectorcd moderate, with 4 short Jingers. Vertehrce 50. 

 Cervical vertehrce sometimes anchylosed. Keui'al canal broad, tri- 

 goncd. Ribs 11 . 11, Balfenopterina, or Beaked Whales, 



8. Bal>s;nopteiia. Second cervical with a broad lateral expansion per- 



forated at the base. First rib single-headed. Lower jaw with 

 conical coronoid process. 



The student must not run away with the idea that, because the 

 characters of the genera here given are taken from a few parts of the 

 skeleton, they are the only differences which exist between the skele- 

 tons of the different genera and species. The form of the head and 

 the pecidiarities of the cervical vertebrae, of the ribs, and of the 

 blade-bone have been selected after a long and careful comparison of 

 the skeletons, as the parts which afford the most striking characters, 

 that can be most easily conveyed to the mind of the student in a few 

 words, and therefore best adapted for the distinction of the genera 

 and species. 



The careful examination of many skeletons has proved to me 

 that almost every bone of each genus is peculiar — that is to say, that 

 no bone is exactly alike in any two genera ; but the difference be- 

 tween them is often very slight, so slight that it would be almost im- 

 possible to convey an accurate conception of it to the reader by words 

 alone, yet it is permanent and characteristic. Though the same 

 bones of the different skeletons of the same species of Meijnptera or 

 Physalus which I have examined offer a certain amount of variation 

 in minor particulars, yet almost every bone of each species has a 

 character of its own; so that a person conversant with the subject, 

 and fresh from the study and comparison, can say at once to which 



