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 1^" 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, l^" long and rather less than ^" 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 eacli 

 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 

 wanting. 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 (bh) 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 45" 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. 2 z 



