240 



MKKISTK 1 VAl;IATI<>\. 



[PART r. 



326. 



327. 



*328. 



definitely tin- extra tooth. The first pi. -molars of each side are almost 

 exactly alike, and tin- .-eeond an. I third of the left side are each very 

 liki- tin- second ..n tin- right side (jr), so that it might be said that //-' 

 was represented l>y two teeth on the left side; and as seen in Fig. ">* 

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

 jaw. as tin- normal IT would do. This is however accomplished by the 

 liack \\ard displacement of ^5. Probably therefore this should be looked 

 on as a case of division of 1^, but there is no proof that the three first 

 premolar.s ,f tin- left side are not collectively equivalent to the tir-t 

 two ..f tli.- ri-Jit side. C. M., 911, f. 



P. groenlandica : the second upper right premolar is represented 

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

 same le\el in the arcade, the inner one being rather smaller. On the 

 li-t't -id.- the second uppei- premolar is incompletely double, the crown 

 I.ein^ partially divided by an oblique constriction into an anterior and 

 internal pun imi and a larger posterior and external part. The former 

 has uiie mut and the latter two. P. M.., A, 2897. 



Otaria jubata : left upper y/ :i a bigeminous tooth something like 

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

 the preniulai-s and molars are one-rooted and have simple conical 

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

 teeth imperfectly <li\ide<l 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 wT 1 is much 

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

 posit iun .if sum.- of the teeth is not very certain, but the above- 

 mentioned t'aets are correct. C. 8. M., 97-X 



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

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



l'i... .v.i. 

 teeth, Mini 



itturin cinerea, N<>. H28. A diagram of the positions of the upper 

 <>f the tn-th standing inti'iiial to each we\ 



~'th tooth behind the canine (sc. "/'). which is pushed outwards by it. 

 The extra tooth of the left side ( Ki-. .V.I) is a little larger and at a level 

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



