138 MR. W. K. PARKER ON THE STRUCTURE 



part of the alinasal fold. These South- American types agree together in the very 

 limited ossification of the nasal sacs, so different from the Old-World Rapaces. 



In the King Vulture (Sarcorhamphus papa) the palate agrees with that of its con- 

 gener Cathartes (Plate XXV. fig. 19) ; but I find a small medio-palatine (mpa), and 

 also much larger and more functional basipterygoids (bpg). In this bird the Eustachian 

 passages (eu) open out into a very patulous, triangular fossa; and all the basicranial 

 structures are very strongly soldered together. The basitemporals (bt) have also a 

 large mammillate knob on each side for muscular attachment. 



On the Structure of the Skull in the Owls (Strigidse). 



The Owls are the most distinct group of the Rapaces, and in respect of their basis 

 cranii come very naturally after the Cathartidse. They agree with the Cariama in their 

 digestive organs, and, what is also quite unaccountable, with the Pigeons, in having a 

 curious deficiency in the occipital arch, a hole, like an artificial pin-hole, being left unos- 

 sified, as it was formerly non-chondrified, over the great cranio-spinal opening. The study 

 of the skull of the Owls in nestlings and young fledglings is of great interest, these ob- 

 servations being made before the skull has become one light, spongy, undivided mass. 



In a fledgling of the Barn-Owl (Ahico flammeus) the details can be well made out 

 (Plate XXIV. fig. 5), and the likeness and unlikeness of the type to that of the highest, 

 the Palcon (fig. 4), and the lowest, the Cariama (fig. 3), is clearly seen. 



The relation of the pterygoids to the basipterygoid processes (pg, bpg) is quite like what 

 is seen in the King Vulture ; but the parasphenoid (pas) is very swollen and is early fused 

 with a very thick and spongy interorbital septum. Not only are the outworks of the 

 ear of larger extent, but the tympanic cavity has large " anterior recesses " and great 

 upper chambers, corresponding to the open gallery that connects the right and left 

 chamber in the Crocodiles. The Barn-Owl has a chain of small tympanic ossicles, six 

 on each side, running along the inferior surface of the junction of the " lower otic pro- 

 cess " of the quadrate and the wing of the prootic, to which it is articulated. 



This lower otic process is as large relatively, and as divergent inwards from the 

 " upper otic process," as in the Prog ; it turns, however, more backwards than in the 

 Batrachian. 



The orbital process, or blunt-pointed free pedicle of the mandibular suspensorium (qua- 

 drate), is far severed from the trabecular base, and turns forward as well as inwards. The 

 rest of the mandibular arch is feeble; its united halves form an acute angle in Aluco 

 flammeus, and a much wider angle in Asio and Strix. So it is with the palate, this part not 

 being nearly so outspread in Aluco flammeus as in the other types. Still in this species 

 the pterygoids (pg) diverge very much, and articulate with basipterygoid processes 

 (bpg) very far apart, on the massive parasphenoid (pas). The pterygoids are slender, 

 sigmoid, and cultrate ; they are toothed in front, and have a small epipterygoid crest (epg) 

 behind. In this species the palatines (pa) are almost parallel, and they are very contrary 

 to most of the bones, being thin and lathy. In this species the palatines are as simple 

 as in the Common Powl, the transpalatine process being suppressed, and the muscular 



