742 MR. COLLETT ON THE SKULL OF STRIX TENGMALMI. [Dec. 5, 



below the middle. In Stria; otus and S. brachyotus, however, it is 

 almost entire and without any incision. But in &. tengmalmi there 

 appears the peculiar extension, already mentioned, which reaches in 

 front of the ear-openings and bends downwards and finally inwards. 



This process in the ' crista' proves to be only asymmetrical in ap- 

 pearance, extending on the one side (where it is itself shorter than 

 on the other) far more downwards than on the opposite side. On 

 close examination it will be found that this process projects on both 

 sides to an equal distance from the upper end of the ' crista ;' and 

 having the same length and curvature on each side, it consequently 

 terminates higher up on the right side (where, as has been said, the 

 ' crista ' is longer) than on the left (where the ' crista ' is shorter). 

 The apparent asymmetry of this process is therefore not due to its 

 own structure, but to the ' crista ' itself. 



While this extension of the right prolonged ' crista ' bends for- 

 wards, downwards, and finally inwards, above the ' os jugulare,' and 

 touches with its rounded extremity the lowest and outer edge of the 

 ' processus orbitalis posterior,' it bends on the left side (which is 

 shortened) beneath the ' os jugulare ' and widens at its extremity into 

 an oblong ' condylus,' which fits into and articulates (sometimes 

 feebly but yet plainly) with a corresponding surface on the ■ os coro- 

 noideum maxillae inferioris,' jointly with the normal 'os quadratum' 

 and ' os jugulare.' The * cranium ' in this way comes into immediate 

 contact with the lower jaw (as seen in fig. 4, p. 740). 



As to the other parts of the ' os squamosum,' it may be said that 

 the * processus zygomaticus ' is but very feebly developed. The 'pro- 

 cessus orbitalis posterior ' seems in this species (as appears also to be 

 the case in young examples of Strix aluco) to be formed solely of the 

 'os alisphenoideum ;' but, as in all the Strigidcc, it is very strongly 

 developed, forming a considerable part of the outer side-wall of the 

 orbit, and bending down, like a flattened sharp-ending nail, before 

 the ' os squamosum,' without (as is the case in S. flammed) reaching 

 the ' os jugulare.' 



The precise nature and extent of any asymmetry in the other bones, 

 coalescent with the 'os squamosum,' I am not at present able to 

 point out. That there must be a modification in a slighter degree 

 of the ' os alisphenoideum,' ' os frontale,' and 'os parietale' (espe- 

 cially of the last) is perfectly consequent, and it strikes the eye on a 

 cursory examination of the skull. But for this purpose examples 

 of younger individuals, which I have not yet obtained, are required. 

 An examination of an immature example preserved in the Museum 

 of the University of Christiania, the plumage of which is minutely 

 described in the ' Nyt Magazin for Naturvidenskaberne ' (xviii. 

 p. 161), led to no result, the cranium (on account of its youth) being 

 defective. 



The observations above recorded are based on an examination of 

 nearly a dozen skulls of Strix tengmalmi, all of which have proved 

 to be alike even to the most minute particulars. 



P.S. — Doubtless the nearly allied (if, indeed, specifically distinct) 



