PHYSETERID& 251 



been met with at various distant localities in the Southern Ocean, 

 and also oft' the coast of Madras and in the North Pacific. 



Extinct Physeteroids. Teeth of Physeteroids are of very common 

 occurrence in the Belgian and English Crags, and evidently indicate 

 the former existence of Whales more or less closely allied to the 

 Sperm Whale, but often distinguished by the presence of an enamel- 

 cap on the crowns of the teeth. The generic determination of these 

 teeth is, however, exceedingly difficult, owing to the water-worn 

 condition in which they are frequently found, and also on account 

 of the impossibility of knowing whether small and large teeth may 

 not be referable to different parts of the jaws of the same species 

 or to individuals of different ages. Moreover, in the cases of 

 isolated teeth it is impossible to know how many were contained 

 in the jaws, and therefore to distinguish Physeteroid from Ziphioid 

 teeth. Physeterula is a small form about one-third the dimensions 

 of the Sperm Whale, and distinguished by the length of the mandib- 

 ular symphysis being only about one-third that of the entire ramus ; 

 it is identified by Professor Cope with Cogia. Eucetus (Dinoziphius) is 

 founded on teeth which are regarded as closely resembling those of 

 Physeter, but distinguished by their subcylindrical form and the 

 small size of the aperture of the pulp-cavity. It does not appear, 

 however, to be certain that these teeth are not worn specimens of 

 those described as Scaldicetus. Physetodon, from the Pliocene of 

 Australia, is founded upon the evidence of similar teeth. The teeth 

 from the Belgian Crag described as Scaldicetus are somewhat smaller 

 than those of the Sperm Whale, and are readily characterised by 

 their cap of grooved enamel. Other teeth with enamel -caps have 

 been described as Physodon and Hoplocetus. The genus Balcenodon 

 is founded upon a very imperfect large tooth from the English Crag, 

 which is not sufficiently well preserved to admit of exact comparison 

 with the other types. 



Subfamily Ziphiince. Teeth of the mandible (at least in existing 

 forms) quite rudimentary and concealed in the gum, except one, or 

 very rarely two, pairs which may be largely developed, especially 

 in the male sex. A distinct lachrymal bone. Externally the mouth 

 is produced into a slender rostrum or beak, from above which the 

 rounded eminence formed by a cushion of fat resting on the cranium 

 ' in front of the blowhole rises somewhat abruptly. Spiracle or 

 blowhole single, crescentic, median, as in the Delphinidce. Pectoral 

 fin small, ovate, the five digits all moderately well developed. A 

 small obtusely falcate dorsal fin situated considerably behind the 

 middle of the back. Longitudinal grooves on each side of the skin 

 of the throat, diverging posteriorly, and nearly meeting in front. 

 In external characters and habits the animals of this group closely 

 resemble each other. They appear to be almost exclusively feeders 

 on various species of cephalopods, and occur either singly, in pairs, 



