^ Classification of the Striges. 341 



(4) The interorbital plate is tliiii and often fenestrated. 



(5) The sternum has two notches on either side. 



(G) In the foot the second joint of the third digit is sub- 

 equal in size to the basal joint. 



(7) There is a bony ridge upon the under surface of the 

 upper end of the tarso-metatarsus. 



4. Tensores patagii. — I take this opportunity of noting 

 certain points in the structure of the muscles and syrinx 

 which are quite in harmony with the division of the Striges 

 into two families^ Strigidte and Bubonidte. With regard to 

 the muscles I have to call attention only to the tensor patagii 

 brevis and to the tensor patagii longus. In Bubo the 

 tensor patagii brevis splits into two tendons, which are in- 

 serted on to the fascia of the muscles arising from the elbow. 

 In Strix flammea these tendons are more complicated; the 

 tensor patagii brevis gives rise to two tendons; the inner of 

 these tendons branches, the outer branch fusing with the outer 

 tendon; from the point where the inner branch joins the 

 fascia covering the eflK-muscles a thin tendon passes ob- 

 liquely through the patagium ^join the tendon of the tensor 

 patagii longus. This oblique tendon occurs in -S^. flammea 

 and S. pratincola and (according to a MS; sketch of Prof. 

 Garrod) in S. novan hoUandide ; it does not occur in any other 

 Owl which I have dissected, viz. Bubo maculosus, Scops leucotis, 

 Pulsatrix torquata, Athene noctua, Syrnium aluco, S. nebu- 

 losum, Otus vulgaris, Ketupajavanensis, and Nyctea nivea. For 

 the present, therefore, there is this difference between the 

 Strigidffi and the Bubonidse ; and although it is undoubtedly a 

 small difference, its constancy makes it of some importance. 



As the object of the present paper is not to give an account 

 of the anatomy of the Striges, but to distinguisli the two 

 families Strigidse and BubonidiTe, I have not indicated the 

 numerous minute points of ditlercnce in the disposition of 

 the tensores patagii in the various genera of Bubonidae. 



5. Syrinx. I have examined this organ in the following 

 genera and species : — 



