MORPHOLOGY OF THE OWLS. 31 



wards in the form of a strap-shaped plate, finally meeting the ischium ; at this point it 

 turns abruptly upwards and outwards to meet the postero-external angle of the dorsal 

 plane, and at the same time closes the ilio-ischiadic foramen. This peculiar downgrowth, 

 and its subsequent upgrowth, forms tlie recess in question. Seen from above, the 

 downgrowth leaves an unfilled triangular space immediately behind the hinder border 

 of the ilium which later becomes filled up. The above description is based on the 

 innominate of a nestling Speotyto. In a slightly younger Syr)i'mm aluco the mesial 

 inturned border of Speotyto w^as here twisted so far outwards as to make it appear that 

 the recess was formed rather by an extension backwards of the inner half of the 

 hinder, and not the mesial border of the iKum. Furthermore, the downward extension 

 of the plate, and its union with the ischium, was slightly different, inasmuch as, seen 

 from below, it formed a scroll-shaped mass lying at right angles between the ischium and 

 the long axis of the pelvis. In the adult, not the slightest clue is obtainable of the 

 origin of this recess. 



The ischium has the posterior extremity rounded, not pointed as in the adult, its 

 anterior extremity presents a sharply truncated face to unite with the pubis, and sends 

 upwards a long columnar spur to unite with the ilium, and close the acetabulum 

 posteriorly. The pubis develops from the dorsal surface of its anterior extremity a 

 cylindrical spur, truncated at both ends, which are wedged in between the ischium on 

 the one side, and a descending bar from the preacetabular ilium on the other. 



VIII. The Pectoral Limb. » 



The pectoral limb bears a strong resemblance to that of the Palconiformes. It may, 

 however, be distinguished by the relatively smaller j^ectoral crest of the humerus, 

 the deeply excised postaxial border of Ph. 1, Mc. II, and the fact that the j)roximal 

 end of Mc. Ill fu.ses with Mc. II distad of the extremity of Mc. I. In the Falconi- 

 formes, excepting in the Cathartae, the fusion of Mc. Ill takes place at a point 

 corresponding to a line drawn across the shaft of Mc. II from the distal extremity of 

 Mc. I. The Cathartse agree with the Sti'iges in the last particular. 



The humerus in the Asionidte has a well-developed pectoral crest, rounded in outline, 

 the palmar surface of which, for the insertion of the pectorulis, is generally sharply cut 

 off from the shaft by a well-defined linen uspera. The sulcus transcersus (coraco-humeral 

 groove) is very shallow or wanting, and the incisura capitis is only moderately deep. 

 The tuhercuhmi internus is large, and the tuberculum externus distinct. The pneumatic 

 foramen is large. The crista inferior is only moderately developed. The linea aspera 

 marking the insertion of the deltoideus major extends a considerable distance down the 

 shaft, terminating in a sharp point. The scar for the insertion of the brachialis inferior 

 is linguiform and of considerable length. The shaft is nearly cylindrical, sigmoidally 

 curved, and presents a conspicuously expanded palmar surface, owing to a large, rounded 

 entepicondylar process. Both ulnar and radial trochlese are well developed, and there is 

 a small ectepicondylar process. 



