260 ME. W. P. PYCEAFT ON THE 



aperture is almost circular ; its vertical axis is rather less than the horizontal axis of 

 the eyehd. The cavernuui gradually deepens from aliove downwards and backwards. 

 Its floor is divided into two deep pits by a vertical fold of skin investing the second 

 portion of the temporalis muscle which runs from the postorhital process to the 

 corouoid region of the lower jaw. 



In Bubo nycteus the external aperture is pyriform in shape, the base being directed 

 upwards and sloping oliliquely back^vards ; its vertical axis is equal to the horizontal axis 

 of the eyelid. The cavernuDi is sjjacious, and closely I'esembles that of B. macnlosits. 

 It differs, however, in this respect, that the eye projects more laterally, and has given rise 

 to a shallow depression immediately behind it, at the bottom of which lies the mouth of 

 the cavernulum. 



In Bubo ignavus the aperture is oval, its vertical axis equal to the horizontal axis of 

 the eyelid. The depression beliind the eye just described is here much more marked, so 

 that the cavernum is divisible into an anterior and a posterior portion. It is further- 

 more continued upwards between the skin and the skull to the crown of the head, and 

 backwards between the postaui'al fold and the skull : thus it has gained a considerable 

 increase in size. 



B. virginianiis differs from B- ignavus in that the aperture is somewdiat smaller, and 

 the anterior and posterior divisions of the cavernum still more sharply marked. 



B. maculosus agrees with B. ignavus in the' size of the aperture, but differs from this 

 species and agrees with B. vlrgiuianus in that the cavernum is divisible into two portions, 

 the posterior division being even deeper than in this species. 



Bubo torqimhis agrees with B. virginiaims in the size of the aperture, but more nearly 

 approaches B. muculosus in the form and size of the cavernum. 



Scops and Bubo appear to closely resemble one another in the form of the external 

 ear, so far as can be judged from an examination of two species of the former genus. 

 The posterior division ditfers from that of Bubo in that it extends the whole vertical 

 heirfit of the cavernum instead of being confined to its lower third. 



In S. leucotis the aperture is semilunar, and its vertical axis is equal to the horizontal 

 axis of the eyelid. There is a considerable extension of the cavernum iipwards to the 

 crown of the head, between the skull and the skin, and between the postaural fold and 

 the skull. 



In S. giu the vertical axis of the aperture is only half the horizontal axis of the eyelid. 

 The anterior portion of the cavernum is very shallow, being almost filled by the eye. 

 The transition between the anterior and posterior portions is sudden, aud the latter 

 very deep. The floor is spacious. 



Ninox noccs-zealandice has an almost circular aperture, the vertical axis of which is 

 nearly equal to the horizontal axis of the eyelid. The cavernum closely resembles that 

 of Scops. 



In Sceloglau.i: albifacles, so far as I could make out from a relaxed skin (p. 244). the 

 aperture of the ear was semilunar, equal to, and probably greater than, the horizontal 

 axis of tIic eyelid, iiazardiug a guess, I should say that the cavernum probably most 

 closely resembled that of Bubo. Mr. J. H. Gurney (7), after the examination of a 



