274 ME. W. p. PYCEAFT ON THE 



Plate 26. 



Figs. 1, 2, 3, 4, 5. Dorsal views of Nyctala Temjmalmi, Speohjto cunicularia, Scops leucotis, Bubo 

 711/cteus, and Bubo mactilosvs, to show the form of the spinal tract. — Note the upward extension 

 of the apt. coll. Lit. in B. maculosus. 



Fig. 6. Ventral view of Syrnium aluco to show the form of interramal area and the pt. ventralis. 



Letters as before. 



Plate 27. 



Fig. 1. Left side view of the head of an adult Asio otus, to show the form and great size of the external 

 aperture of the ear. This should be compared with tig. 2 — the right side of the same head- 

 to show the asymmetrical development of the two sides, and with fig. .3 opposite, to compare 

 the differences between A. otus and A. acripiirinHS . 



d Diverticulum. 



M Mandible. 



M. e Meatus externus, s. via recta, p. 262. 



Op Operculum s. preaural fold. 



P. f. Postaural fold. 



R Rim. 



S Skull. 



The cavcrnum (p. 259) includes the whole space surrounded by the pre- and postaural folds ; the 

 portions M.e. and d. separated one from the other by the valve represent the posterior division of the 

 cavernum of Bubo and Scops. 



Fig. 2. Right side view of the same head. Letters as before. 



Fig. 3. Left side view of the head of an adult Asio accipitrinus, to show the form of the external ear. 

 Compare with fig. 1 to make out the diftcrcnccs between this and A. otus, and with fig. 4 to 

 make out the asymmetrical development of the two sides. — Note the presence of a postorbital 

 tubercle, affording support to the valve. This is wanting in A. otus. 

 * Postorbital tubercle. 



Fig. 4. Right side of same head. Letters as before. 



Fig. 5. Left side view of the head of an adult Nyctala Tengmalmi, to show the form of the external 

 aperture of the ear. This should be compared with fig. 6, the right side view of the same head, 

 to note the very asymmetrical development of the skull-boues on the two sides of the head. 



t. w. sq Tympanic wing of the squamosal. 



q. j Quadrato-jugal. 



Fig. 6. Right side view of same head. Letters as before. 



Fig. 7. Anterior view of the skull of Nyctala Tenynialml, from a specimen in the Cambridge Museum' 

 of Zoology, to show the asymmetrical arrangement of the skull-bones. 

 P. o. p Postorbital process. 



Plate 28. 



Fig. L Left side view of the head of an adult Syrnium aluco, to show the form of the external aperture 

 of the ear. Compare with fig. 2 — the right side view of the same head — to show the 

 asymmetry in the size of the two apertures ; and with fig. 4 to show the difi'erence between 

 the ears of R aluco and Stria: flammea. 



D Peripheral disc-feathers. 



