Order CETACEA.
Reading edition
Teeth all similar, conical, sometimes not developed. Palate 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.—Balænidæ, Catodontidæ, Susoidea, Orcadæ, Belugidæ, Pontoporiadæ, Hyperoodontidæ, Epiodontidæ, Ziphiidæ.
II. Pectoral fin elongate, obliquely truncated on the inner side; fingers 5, elongate, longer than the arm-bones, the second and third much longer than the rest.—Iniidæ, Delphinidæ, Grampidæ, Globiocephalidæ.
III. Pectoral fin elongate, truncated on the inner side; fingers 4, subequal, more or less elongate.—Agaphælidæ, Megapteridæ, Physalidæ, Balænopteridæ.
By the adhesion or non-adhesion of the cervical vertebræ, thus:—
1. Atlas distinct, the other six cervical vertebræ united by their bodies and spines into a single mass.
Mysticetes.
Denticetes.
Catodontidæ.
Grampidæ.
2. Atlas and cervical vertebræ all united into one solid mass.
Balænidæ.
Balænopteridæ.
Physeteridæ.
Hyperoodontidæ
(?) Ziphiidæ.
3. The atlas, axis, and generally one or two other vertebræ united; the hinder ones sometimes free.
Megapteridæ.
Epiodontidæ.
? Ziphiidæ.
Delphinidæ.
Globiocephalidæ.
Orcadæ.
4. Atlas and the other cervical vertebræ entirely free.
Physalidæ.
Agaphelidæ.
Platanistidæ.
Iniidæ.
Pontoporiadæ.
Belugidæ.