152 SHUFELDT. [Vol. XVII. 



border of the right side, as has already been pointed out above, 

 a disposition to approach the asymmetry which is present in 

 S. lapponimni. 



The difference seen in the two sides is better marked in 

 the crania of some specimens than it is in others, and can 

 in the adult individual vary between i and 2 mm., this differ- 

 ence being interesting rather than remarkable, inasmuch as it 

 is just here that in 5. lapponicimi such decided asymmetry is 

 present. This difference can best be appreciated when the 

 cranium is viewed from above (see Fig. 4), although even then 

 it is seen to be very slight, though it is invariably present. 



The occipitale superins {squama occipitis) has no supraoccip- 

 ital foramen. 



The pterygoid bojies are, as in S. aluco, broad in front of the 

 basipterygoid processes, and quite compressed. 



The palatine bones are, comparatively speaking, narrower 

 than in S. aluco ; pars plajics on os ethmoides reach a little 

 beyond the outer margin of either palatine, when the cranium 

 is viewed from below. 



Vomer is almost rudimentary, inasmuch as it is present only 

 as a thin osseous spicula posteriorly, and non-ossified in front. 



Maxillo-palatines are very large, and meet in the line below. 



9. Syrnium lapponicum (Thunb.), 1789. 



(Plate XIX, Fig. 27 ; Plate XX, Figs. 28-30. Text-figs. 5-7.) 

 Auricular openings ; ear-flaps ; and cranium asymmetrical. 



The dermal parts of the auricular openings, structurally, 

 about agree with the two other species of Syrniiini and present 

 a similar asymmetry. Upon the whole, they are quite large, 

 being subequal in size, although this asymmetry is apparently 

 less than in .S. aluco. 



Upon the right side, where they are of the greater size, the 

 ear-opening has in an adult female specimen (collected in 

 East Aker, Nov. 17, 1881) a vertical height of 30 mm. and 

 a width of 15 mm.; on the left side the height is 28 mm. 

 and the width 14 mm. They may be said to be placed high 

 up on the side of the head, being situated just back of the 



