8 ARKIV FÖR ZOOLOGI. BAND 12. NiO 13. 



magellanicus. The same is also apparent from the condition 

 of other areas of insertion of this musculature. With regard 

 to the extension ' and development of musculi temporales of 

 Ps. lycoides it is of interest to note that they evidently 

 ha ve reached higher up and grown further forward on the 

 left than on the right side in all three skulls belonging to 

 this museum. Cristce frontales externce (== linece semicirculares) 

 which in all are well developed, and rather strongly raised, 

 thus approach the median line more on the left than on the 

 right side. In the largest specimen this crest has on the 

 left side even reached sutura frontalis for a length of 14,5 

 mm in front of the anterior end of crista sagittalis. This 

 peculiar arrangement indicates a rather stränge one- sided 

 use of the jaws. As far as I can remember, I have not seen 

 anything like this^ in any member of Canidce before, although 

 it has been observed that some other mammals chiefly use 

 the organs of one side more than those of the other, as I 

 have stated with regard to the horns of the giraffes, the 

 tusks of African elephants etc. 



In the above it has been discussed, whether Pseudalopex 

 lycoides possibly has been developed to its present superiority 

 in size, and differentiated from its northern relatives on the 

 island of Tierra del Fuego, since it had arrived there. An- 

 other possibility, may, however, also be considered viz. that 

 it has immigrated from the north, as it is, and that those 

 members of the race which remained on the continent either 

 have been exterminated, or degenerated in size, so that they 

 now are represented by the comparatively small Pseudalopex 

 magellanicus and related races of the present time. There is 

 really a fact which strongly speaks for such a hypothese. 



In the year 1908 Erland Nordenskiöld published a 

 description^ of some fossil mammals which he had found in 



^ K. ToLDT jun. has carefully described (Zool. Anz. XXIX, 1905, p. 

 176 — 191) an asymmetrical development of musculi temporales of a common 

 fox, but this was a single and a pathological case and thus not directly 

 comparable. It was caused by the sickly condition of the left lower 

 carnassial. By this the animal had been induced to use the right side of 

 the jaws more, and aecordingly the temporal muscles of that side had 

 been stimulated to a stronger growth, while those of the left side had been 

 left behind. In the skulls of P. lycoides on the other hand I have not 

 been able to see any anomalies, or any pathological conditions. The teeth 

 especially the grinders are a little (but not much) more worn on the left 

 side, that is all. 



' Ein neuer Fundort fiir Säugetierfossilien in Peru. Ark. f. zool., 

 Bd. 4, Nr. 11. 



