No. I.] THE CRANIUM IN THE OWLS. I^y 



exhibits only a single, limited, thin (semitransparent) area just 

 above the sphenoidal rostrum. 



The structure of the osseous crest of the os squamosum cor- 

 responds exactly with what was found in A. accipitrinus, but, 

 inasmuch as the truncated portion of the frontals posterior to 

 the orbits is more extensive than it is in that species, and the 

 big orbital wings (on os alisphenoides) being, as a consequence, 

 situated further forwards, the distance between the osseous 

 crest and the orbit is greater, and the fossa thus created, more 

 capacious, particularly above, than A. accipitrinus. 



The supraoccipital [squama occipitis) is pierced by an ex- 

 tremely minute supraoccipital foramen, which, as in the spe- 

 cies just mentioned, is situated at the base of a little oblong 

 fossa, and in some individuals it doubtless will be found to be 

 absent. 



The pterygoid bones seem to be somewhat narrower than 

 they are in A. accipitrinus and offer a less extensive articular 

 surface for the palatines than in that species. The palatine 

 bones are perhaps a little broader than in A. accipitrinus ; pars 

 plana of the mesethmoid barely passes beyond the external 

 border of the palatine, upon either side, when the cranium is 

 viewed upon its nether aspect. Vomer present, and developed 

 as in A. accipitrinus. The inaxillo-palatines are large and 

 come near being in contact in the median plane of the skull.^ 



7. Syrnium aluco (Linn.), 1766. 



(Plate XVII, Figs. 13, 14. —Plate XVIII, Figs. 17-20.) 



Ear-openings, as well as the ear-flaps, asymmetrical ; the cranium sym- 

 metrical. 



The dermal parts of the auricular openings are of subequal 

 size, and they possess asymmetrical flaps. These openings are, 

 upon the whole, wide ; their borders giving them a reniform, 

 or oblong bean-shaped, outline ; on the right side, where the 



^ While this translation was being made, I have had before me a complete 

 skeleton of Asio wilsoniafius [Asio Brisson ; Strix otus Linn.), collected by me at 

 Fort Fetterman, Wyoming, in April, 1881, and I find the characters it presents 

 agree, in so far as the skull is concerned, with the corresponding ones so correctly 

 given above by Professor Collett for Asio otus. — R. W. S. 



