240 



MEMSTIC VARIATION. 



[part I. 



* 



definitely the extra tooth. The first premolars of each side are almost 

 exactly alike, and the second and third of the left side are each very 

 like the second on the right side (p 2 ), so that it might be said that p 2 

 was represented by two teeth on the left side; and as seen in Fig. 58 

 the second and third on the left side bite between f- and p of the lower 

 jaw, as the normal p 2 would do. This is however accomplished by the 

 backward displacement of p*. Probably therefore this should be looked 

 on as a case of division of P^, but there is no proof that the three first 

 premolars of the left side are not collectively equivalent to the first 

 two of the right side. C. M., 911, f. 



326. P. grcenlandica : the second upper right premolar is represented 

 by two teeth, each of which has two roots; the two teeth stand at the 

 same level in the arcade, the inner one being rather smaller. On the 

 left side the second upper premolar is incompletely double, the crown 

 being partially divided by an oblique constriction into an anterior and 

 internal portion and a larger posterior and external part. The former 

 has one root and the latter two. P. M., A, 2897. 



327. Otaria jubata : left upper p 3 a bigeminous tooth something like 

 the anterior premolars of Ommatophoca (No. 320). In this animal all 

 the premolars and molars are one-rooted and have single conical 

 crowns. The abnormal tooth is formed as it were of two such simple 

 teeth imperfectly divided from each other through their whole length, 

 the plane of division being transverse to the jaw. The teeth of the two 

 sides are not alike and in particular the posterior lower m} is much 

 smaller than the right. The skull has been much mended and the 

 position of some of the teeth is not very certain, but the above- 

 mentioned facts are correct. C S. M., 975. 



oZo. Otaria cinerea : supernumerary tooth in upper jaw on both sides. 

 The extra tooth in each case stands within the arcade, internal to the 



Fig. 59. Otaria cinerea, No. 328. A diagram of the positions of the upper 

 teeth, and profiles of the teeth standing internal to each m*. 



5th tooth behind the canine (sc. »^), which is pushed outwards by it. 

 The extra tooth of the left side (Fig. 59) is a little larger and at a level 

 rather anterior to that of the left extra tooth. C. M., 911 **. 



