248 MEMSTIC VARIATION. [part I. 



5 skulls without lower jaws, and 1 lower jaw without skull ; ab- 

 normals 2, as follows : 

 *366. A young skull having in the upper jaw on the left side 

 (Fig. 62, I.) two teeth, both apparently in place of left j?, making 



»|jE|. B.M., 314,0. 



*367. A specimen having four incisors in the right lower jaw, the 

 left being normal. Perhaps the two hindmost of the four repre- 

 sent the third lower incisor of the left side in the way suggested 

 by the dotted lines in the figure (Fig. 62, II). B. M., 314, b. 



Phalangerid^e : incisors (negleeting " intermediate " teeth of 

 lower jaw) normally |- ; this seen in 209 skulls of various genera and 

 species. 



368. Phalanger orientalis, Solomon Islands: left £ 3 as an imperfectly double tooth, 

 having two sub-cylindrical crowns and only one root (Fig. 63). The two crowns 



Fig. 63. Phalanger orientalis. No. 368. 



Upper incisors and canines. The separate figure shews the left i 3 extracted. 



stand in the same transverse plane, the one being internal to the other and rather 

 smaller than it. Lower jaw missing. B. M., 1936, c. [Two other skulls from same 

 locality normal.] 



369. P- maculatus, Port Moresby: only tico incisors on each side in the upper jaw. 

 The centrals, £, of each side, are in place; externally to them there is on each side 

 an alveolus for a tooth, which, judging from the size of the alveolus, was probably &. 

 Immediately behind these alveoli the canines follow on each side. In this case it 

 may be said that the missing teeth are & in all probability. Lower jaw normal. 

 B. M., 79. 3. 5. 8. 



370. Specimen having "in each upper jaw two incisors instead of three," [also has 

 no left pj, see No. 377]. Leyd. Mus., 55. Jentink, F. A., Notes Leyd. Mus., 1885, 

 vn. p. 90. Two specimens, Leyd. Mus., 56 and 61 are without f of right upper 

 jaw, ibid., p. 91. Specimen in which "five of the upper incisors are wanting [only 

 one "intermediate" tooth in left lower jaw, see No. 377]. Leyd. Mus., 63, ibid., p. 91. 



371. Pseudochirus forbesi: of this species only a single skull known; it has no 

 upper f [and no upper first premolar, see No. 379]. B. M., 1943. Thomas, 0., Cat. 

 Marsup. Brit. Mus., 1888, p. 183. 



(2) Premolars, and the " Intermediate" teeth (in the lower jaw) of 



Phalangerid^e. 



The evidence here offered relates to the following genera : — 

 Phalanger, TricJiosurus, Pseudochirus, Petauroides, Dactylopsila 

 and Petaurus. Before speaking of the variations seen, a few 

 words are needed in explanation of the nomenclature adopted. 



