No. I.] THE CRANIUM IN THE OWLS. 1 57 



The maxillo-palatines are unusually large, and are in contact 

 in the mesial plane, below. 



10. Nyctala tengmalmi (GmeL), 1788. 



(Plate XIX, Figs. 21-26.) 

 Auricular openings and iiaps asymmetrical ; the cranium profoundly so. 



The dermal parts of the auricular openings are nearly of 

 equal size upon the two sides, but in other respects exhibit 

 an asymmetry that agrees with the asymmetry assumed on 

 the part of the cranium itself ; they are very large, occupying 

 as they do the whole side of the head, upon either side ; they 

 are somewhat semilinear or oval in outline, but less pointed 

 above and below than in Asio, and therefore not as gill-slit-like 

 as in that genus. Their vertical height in an adult specimen 

 (collected at Hamar, Sept. 20, 1876) is about 28 mm., the 

 greatest inner width being about 1 2 mm. ; but they frequently 

 have a greater width than this. 



Either of these openings extends from beneath the mandible 

 or lower jaw (close to the mandibular commissure) up to the 

 side of the frontal region, where the space separating the one 

 from the fellow of the opposite side is comparatively wide, 

 being but a little less than the height of either ear-opening. 

 The ear-flap that closes the aural aperture in front is of a semi- 

 lunar outline, but is not very broad, as at a point opposite the 

 center of the eyeball it barely exceeds 6 mm. ; in the frontal 

 region, and below the eye, it is a little broader. Posteriorly the 

 opening is closed by a very well developed integumental fold 

 resembling an ear-flap, which, with a breadth coequal with that 

 of the true ear-flap, extends the entire length of the auricular 

 opening, and both above and below indistinguishably merges 

 into the ear-flap proper. Thus the entire aural aperture is 

 surrounded by a continuous, free, and rather high dermal fold. 

 The contour assumed by this posterior integumental fold is 

 that given it by the form of the cranium ; thus it is high on 

 the right side, and comparatively as low on the left, where the 

 osseous crest of the os squamosimt holds such an abnormally 

 low position. 



