THE SPERM WHALES, GIANT AND PYGMY. 121 
dered easy by the recent publication of a very elaborate mon- 
ograph “On the Osteology of the Cachalot or Sperm-whale 
(Physeter macrocephalus),” by Professor Flower of the 
Royal College of Surgeons of England, and a full descrip- 
tion and illustrations of a pygmy whale, by Professor Owen, 
who has been the first to clearly elucidate the details of 
structure of a member of the group of small species. 
1. Families of Toothed Cetaceans. There are four families 
of toothed cetaceans: the Physeterids, or sperm-whales ; the 
Ziphiids, nearly allied to the former, but in some respects 
approaching nearer to the Delphinids; the Platanistids, 
containing mostly fresh-water forms; and, finally, the Del- 
phinids, containing by far the largest number of genera 
and species, and embracing the dolphins (not the fishes of 
that name), the porpoises, etc. It is on a comparison be- 
tween the members of all those families that the following 
characters are shown to be peculiar, either absolutely or in 
combination, to the Physeteride. 
2. Common Character of Sperm-whales. The form is 
variable, the head being either disproportionately large and 
blunt in front, with a subterminal blower, as in the giant 
whales, or conical, as in the dwarfs; the snout, however, 
always projects forwards, and the mouth is inferior. The 
cervical vertebre in whole, or the atlas excepted, are an- 
chylosed together. The hinder ribs lose their heads, and 
are only connected by their tubercles with the transverse 
processes of the vertebrze. The costal cartilages which con- 
nect the ribs with the sternum retain more or less of their 
original cartilaginous condition. The skull has the bones 
raised so as to form a more or less elevated retrorsely convex 
crest behind the anterior nares. The supraoccipital (so) and 
parietals combined extend forwards on the sides, and pre- 
sent a convex border projecting forwards high above the 
temporal fossa, and forwards beyond the vertex. The 
frontal (f) bones have an extended lateral surface de- 
flected downwards and produced upwards, exposing to view 
