198 DR. J. E. GRAY ON BRITISH CETACEA. [May 24, 
Suborder I. CETE. 
Skin smooth, bald. Teats two, inguinal. Limbs clawless; the 
fore limbs fin-shaped ; hinder limbs united, forming a forked hori- 
zontal tail. Nostrils enlarged into blowers. Carnivorous. 
The size of the head, compared with that of the body, varies greatly 
according to the age of the specimen. In the newly-born whales 
the head is small; and it enlarges regularly, but at a more rapid 
rate than the body, as the whale increases in size. In the Green- 
land Whale, the adult head is two-fifths of the length of the body. 
Sect. I. Mysricetr. Palate furnished with transverse fringed 
horny plates of baleen or whalebone. Teeth none in adults. 
Head large, depressed. Nostrils separate, longitudinal. Gullet 
very contracted. Tympanic bones large. Lachrymal bone 
none. Living on Mollusca and fish. 
The skulls of the different genera differ considerably in external 
form, from being nearly as wide as the lower jaw, as in Sibbaldus, 
to being very narrow so as only to form a narrow central arch, as in 
Balena. The genera may be thus arranged according to the width 
of the skull:—1. Siédaldus. 2. Balenoptera (Gray, Zool. E. & T.). 
3. Rorqualus (Rudolphi, Berlin Acad. 1829). 4. Megaptera 
(Eschricht, Nord. Hvaler, t. 3. f. 2). 5. Physalus (Eschricht, /. ¢. 
t.3.f.3). 6. Eubalena (Cuv. Oss. Foss.). 7. Balena (Eschricht, 
Ue Gertu on tel) 
The width chiefly depends on the lateral expansion of the maxilla. 
In Balena it is band-like ; and in Sibdaldus very broad, being more 
than twice as wide as the intermaxillary bones. 
Fam. 1. BALZNID&. 
Dorsal fin none; belly smooth; baleen elongate, slender. Ver- 
tebree of neck anchylosed. Pectoral fin broad, truncated at the end. 
Tympanic bone rhombic. Maxillary bones narrow, linear, rounded ; 
the maxilla narrow, linear, rounded. Lower jaw with only a rudi- 
mentary ramus. Scapula higher than wide, with a distinct coracoid 
rocess. 
me They roar like an enraged bull. The females are generally the 
largest’ (Beal, 13, 14). 
As the elongated form of the periotic bones and the more or less 
rhombic form of the tympanic bone are characteristic of the Right 
Whales or the family Balenide, so the tympanic portion of each spe- 
cies has a peculiar and specific form, and may be used for the specific 
character of the species, in the same manner as I have shown, in the 
‘Zoology of the Erebus and Terror,’ that the existence of several 
species of Right Whales may be proved, and, indeed, the species cha- 
racterized, by the form and the internal structure of the baleen. 
Unfortunately, when species are determined from these charac- 
ters, the outer form of the animal is unknown; and, unless the 
ear-bones and baleen are obtained from the same specimen, there is 
