222 PEOFESSOE FLOWEE ON THE EECENT ZIPHIOID WHALES. 



upper margin from the apex for two thirds the length of the ramus, to opposite the 

 entrance of the wide infundibuliform dental canal on the inner side. Just before its 

 posterior termination this groove becomes wider and deeper than elsewhere ; behind it 

 the superior edge of the ramus rises into a sharp elevated crest, terminating behind 

 in the feebly marked coronoid process. 



At the anterior extremity of the ramus the groove dilates into a large, oval, narrow, 

 alveolar cavity, 2 - 7 inches long, 1 inch wide and 2 inches deep. Two and a half inches 

 behind this is another, smaller alveolus 1*8 long, 0*6 inch wide in front, and very narrow 

 behind. The floors of both these cavities slope backwards and upwards; and their 

 openings are directed forwards. 



Teeth. — Each of the above-mentioned alveolar depressions contains a tooth, which 

 very nearly fills the socket, and projects but slightly above the level of the upper- 

 surface of the ramus of the jaw. 



The anterior tooth of the left side, although loose in its alveolus, cannot be removed 

 from it as long as the bone is intact. The right tooth, however, was extracted without 

 much difficulty (see PI. XXIX. fig. 7). It is compressed laterally to the form of a 

 nearly equilateral triangle, with a base, an apex, and an anterior and a posterior margin. 

 The base is 2-8 inches long, the anterior margin 2-8 inches, the posterior margin 3 - 2 

 inches, the height from the middle of the base to the apex 3 inches, the greatest thick- 

 ness between the lateral surfaces - 8 inch. The pulp-cavity is completely closed below, 

 the base being rounded and rugose. The inner surface is concave, the outer one slightly 

 convex in both directions. Both surfaces are marked with irregular shallow furrows 

 and ridges running in a longitudinal direction, or rather radiating from apex to base. 

 The apex itself is conical, with a deep linear longitudinal groove on the middle of 

 its inner side ; it appears to be formed of dentine, without any enamel covering, and 

 projects for a distance of 0-3 inch from the mass of cementum which covers the greater 

 part of the tooth. The extremity is somewhat polished, but presents no distinct signs 

 of wear. 



The left tooth, as far as can be seen without removing it from the alveolus, exactly 

 resembles the right. The apex projects scarcely one inch above the level of the alveolar 

 border ; so that before the gum was removed very little, if any, of the tooth could have 

 been exposed. 



The second tooth (PI. XXIX. fig. 8) fits very well into, and nearly fills its alveolus ; 

 but, owing to the form of its root, it is readily removed. It also is compressed and 

 triangular, but narrower from before backwards than the other. Its base is closed ; 

 and its apex is formed, as in the other, of a small cone of dentine, emerging out of an 

 enveloping mass of cement ; the anterior margin is thicker, more rounded and curved 

 than the posterior. The whole tooth lies very obliquely in its alveolus; so that the 

 posterior margin is nearly horizontal, and the apex projects forwards. Such a very 

 small portion is raised above the level of the alveolus, that we might naturally infer 



