296 Prof. A. Nehring on Myodes lemmus crassidens. 



material Myodes olensz's appears to be the most robust. At 

 least two skulls of this species before me, from Nova Zembla> 

 which I was allowed to prepare from two spirit-specimens in 

 our Natural History Museum *, exceed in size the largest 

 skull of Myodes lemmus which I have. Their basal length 

 ("Basilarlange/' Hensel) averages 30'5 mm., their total length 

 (exclusive of the incisors) is 33-3 and 33 mm. respectively, 

 their jugals 24 and 22-8 respectively, and the length of their 

 rows of upper cheek-teeth 8*5 mm. In addition, these skulls 

 are surprisingly thick. A third skull of M. ohensis, which I 

 have taken from a North-Siberian skin in our collection (at 

 the Berlin Hochschule), is much more elegant, but doubtless 

 belonged to a younger animal f- 



According to Lilljeborg (' Sveriges och Norgea Ryg- 

 gradsdjur,' i. Upsala, 1874, p. 325), the normal length of the 

 skull in M. lemmus should be 32 mm., and the breadth across 

 the zygomatic arches 22 mm. ; but the ten skulls now before me 

 are all smaller, having a total length of from 28 to 30-8 mm., 

 and a breadth of 19 to 21 mm. across the zygomatic arches. 

 A skull, in my own collection, of an old male from Finland, 

 the strongest and most massive of all the skulls of M. lemmus 

 at my disposal, has a total length of only 30*8, and a breadth 

 across the zygomatic arches of 21 mm. From this I must 

 conclude that Lilljeborg's skull-measurements for M. lemmus 

 do not refer to the average, but to the maximum. 



The same appears to be the case with M. schisticolor. 

 Lilljeborg (op. cit. p. 318) gives the length of skull in this 

 species as 25, and the breadth across the zygomatic arches as 

 16 mm.; but in the three examples before me, which can 

 in no way be regarded as immature, but are of medium 

 age, the biggest has a length of only 23*7, and a breadth 

 across the zygomatic arches of 14*5 mm. In the two other 

 skulls the total length averages 22*5, and the breadth across 

 the zygomatic arches 14 mm. | The length of the upper 

 rows of cheek-teeth in all three averages about Q'Q mm. 



The Portuguese lemming skulls from the cave at 

 Athouguia, which I have before me, as already stated, 

 agree almost exactly with the Scandinavian examples lying 



* These specimens (labelled No. 4343), collected by Heuglin, were 

 placed in my hands by Herr P, Matschie, by the kind permission of 

 Herr Mobius. 



t The skull figured by Middendorff (Sibir. Reise, Saugeth. pi. x.) of an 

 adult M. obensis agrees exactly with those before me from Nova Zembla. 



X Besides this, the skull of M. schisticolor differs from that of 

 M. Ummus not only in its elegance, but in the more spherical shape 

 of the auditory bulla. 



