^4 



Order CETACEA. 



Teeth all similar, conical, sometimes not developed. Falate often 

 furnished with transverse plates of baleen or whalebone. Body fish- 

 shaped, smooth, bald. Limbs clawless ; fore limbs fin-shaped ; hinder 

 united, forming a forked horizontal fin. Nostrils enlarged into 

 blowers. Teats two, inguinal. — Carnivorous. 



They may be divided by the form of the pectoral fin, thus : — 



I. Pectoral fin broad, truncated or rounded at the end ; fingers 5, shorter 



than the arm-bones, subequal, gradually shorter in the series. — Bal^e- 



NID^E, CATODONTIDiE, SuSOIDEA, OrCAD^E, BeLUGIDJE, PoNTOPO- 

 RIAD^E, Hyperoodontld^e, EPIODONTID.SJ, Ziphiidje. 



II. Pectoral fin elongate, obliquely truncated on the inner side ; Jmgers 5, 



elongate, longer than the arm-bones, the second and third much longer than 

 the rest. — Iniid-s:, Delphinid^;, Grampid^:, Globiocephalid^e. 



III. Pectoral fin elongate, truncated on the inner side ; fingers 4, subequal, 

 more or less elongate. — Agaphjelid.s:, Megapterid^e, Physalid^e, 



BALiENOPTERID.^:. 



By the adhesion or non-adhesion of the cervical vertebrae, thus : — 



1. Atlas distinct, the other six cervical vertebra} united by their bodies 



and spines into a single mass. 



Mysticetes. Denticetes. 



CATODONTIDiE. 

 GRAMPIDiE. 



2. Atlas and cervical vertebrae all united into one solid mass. 



BALJENID.E. PHYSETERIDJE. 



BaL^ENOPTERID^E. HYPEROODONTIDiE. 



(?) ZiPHiica:. 



3. The atlas, axis, and generally one or two other vertebrae united ; the 



hinder ones sometimes free. 



MEGAPTERIDiE. EPIODONTID^E. 



? ZlPHIIDJE. 



Delphinidje. 



Globiocephalip^e. 



Orcap^. 



4. Atlas and the other cervical vertebra? entirely free. 



PHYSALIBiE. PLATANISTIBJE. 



AGAPHELIBiE. InIID^I. 



PONTOPORIAPiE. 



Belugid.e:. 



