MR. W. H. FLOWER ON THE OSTEOLOGY OF THE SPERM-\WHALE. 325 
skeleton the teeth are all retained in their place by the tough fibrous gum, in which 
they are to a large extent imbedded, and which supplies the place of close-fitting bony 
alveolar walls. Those near the middle of the series are about 5” in length, of which 
not more than 13” projected above the gum in the living animal. The crowns are 
conical, recurved, and pointed, showing but little signs of wear. The pulp-cavity is 
widely open at the base. At the hinder end of the series they become smaller, and 
more pointed; but the last on both sides has a flat and oval crown, scarcely projecting 
above the level of the gum. They are not symmetrically placed in pairs along the jaw, 
and are even unequal in number on the two sides, as there are twenty-eight on the left. 
and but twenty-five on the right. 
In the young cranium presented by Mr. Crowther, obtained from a sucking Cachalot, 
killed by the side of its mother, the teeth were still concealed within the gum. Although, 
unfortunately, most of them had been lost in preparing the specimen, a sufficient number 
were preserved to show their general characters. ‘These are simple, cylindrical, nearly 
straight, obtusely pointed, 13” long and rather less than 3" in their greatest diameter. 
It is interesting to observe that they show no trace of an enamel covering to the apex, 
a point which has hitherto been one of uncertainty. Judging by the alveolar depres- 
sions at the bottom of the dental groove, there appear to have been 24 teeth on each 
side in this specimen. 
The largest jaw from Tasmania, in the Museum of the College, has 25 teeth on each 
side ; two others from the same locality have 26-26 and 24-23 respectively ; and a very 
old jaw, with massive and much worn teeth, locality unknown, has but 21-20; and a 
small, but adult specimen (female ?), has 22-22. The exact number of teeth of the 
Caithness skeleton cannot be ascertained, as the anterior portion of the mandible is 
wauting. Beale gives 24—24 as the number in the Yorkshire skeleton ; but it is doubtful 
whether this statement refers to the actual teeth, or to the wooden models now in their 
place, on which of course it is impossible to place absolute reliance. 
Hyoid Bones. 
The bones of the hyoid arch are very remarkable, not only from their great relative 
size, but especially for the peculiar breadth and flatness of the basihyal (4) and thy- 
rohyals (th) (Plate LX. fig. 1). 
The stylohyals (sh) are large, subcylindrical, and slightly curved, truncated at both 
ends, 25" long, and 4" to 43” in diameter. 
The basihyal and thyrohyals are not ankylosed; and, judging by their opposed sur- 
faces, a considerable space occupied by cartilage must have existed between them. 
These bones are also distinct in the Yorkshire skeleton. The basihyal is nearly flat, 
though the under surface is somewhat concave from side to side, and convex from before 
backwards. It is 17” long and 18" broad. A truncated process projects forward, for the 
attachment of the cartilages connecting the stylohyals: this is not bifid, as in most Ceta- 
VOL. VI.—PART VI. 22 
