SEALS AND IIIIALES OF THE BRITISH SEAS. 



members were formerly distinguished by the absence of functional teeth in 

 the upper jaw, but, recently, a row of small teeth, of determinate number and 

 definite form, has been discovered in many individuals of a species of Mcsop- 

 lodoti. The teeth in the lower jaw are always quite rudimentary, with the 

 exception of one, or occasionally, two pairs. These may be largely developed, 

 especially in the male sex, and are placed, generally, well forward. " They 

 have a small and pointed enamel-covered crown, composed of true dentine, 

 which, instead of surmounting a root of the ordinary character, is raised upon 

 a solid mass of osteo-dentine, the continuous growth of which greatly alters 

 the form and general appearance of the organ as age advances." In Mcsop- 

 lodoii layardi this little dentine cap is not larger than the portion of the tooth 

 ordinarily shown above the gum, but the fang-like growth is so great that the 

 tips of the " tusks" meet over the upper jaw, so that the animal is only able 

 to open its mouth for a very short distance indeed. The form assumed in 

 Mesoplodon bidcns will be seen in the figure of the head of that species, at 

 p. 104. The blow-hole is sub-crescentic, and a pair of remarkable furrows 

 occurs in the skin of the throat, almost in the form of the letter V, the point 

 directed forward. The skull presents a remarkable appearance in the genus 

 Hyperoodon, caused by the enormous maxillary crests which produce the 

 peculiar conformation of the head in the living animal, originating the trivial 

 name " Bottle-head." The food of the whole group is said to consist mainly 

 of Loligo, commonly called " Squid," and other Cephalopods which frequent 

 the open sea. 



One very singular circumstance with regard to these creatures is 

 that they never seem to be taken at sea, but, whenever procured, it is 

 by their running themselves on shore. This, as before remarked with re"-ard 

 to the Sperm Whale, would seem to indicate that their natural habitat is 

 the deep waters of the open seas, where shallows are unknown. The sand- 

 banks which surround a sloping shore, of which they have had no experience 

 speedily prove fatal to them. 



