140 MR. W. K. PARKER ON THE STRUCTURE 



The vomer (v) wedges in between the small ethmo-palatine laminae (epa) ; and above it 

 is a similar bone, the median septo-maxillary (msmx) : both the bones are similar in 

 shape ; but the vomer lies behind the bone above it. In the large Ketupa ceylonensis 

 there are two similar bones (Plate XXV. fig. 11, v, mpa) ; but they are much smaller, 

 and the vomer is in front of the other, which is a medio-palatine. 



In Athene noctua these parts are all coalesced together. The palatine keystone, made 

 carinate by a small vomer, just shows traces of its sutural connexion with the ethmo-pala- 

 tines. This bird has large superorbital processes to its frontals, not to its lacrymals. 



In the Hooting-Owl (Strix stridula) these parts remain separate (Plate XXV. figs. 20, 

 21). There is a small vomer (v), and over it a similar bone, as in Asio otus ; both of these 

 arrested bones are in front of the short ethmo-palatines (epa) ; but behind these there 

 is a veritable medio-palatine (fig. 20, mspg, fig. 21, mpa) * ; and the antero-superior 

 ossicle (msmx) has the same position as the small median bone which I have called 

 the "median septo-maxillary" in the Harrier (Circus cyaneus). 



This is the bone which may possibly be a rudiment of the vomer of the other side 

 (right or left); for in the "Picidse," certainly, I have seen submesial bones join the mid 

 line ; and the stronger push the weaker out of place. 



In none of the Eapaces have I seen any remains of the paired " septo-maxillaries " so 

 common in the Passerinse, where they are small (although so large in Ophidia and Lacer- 

 tilia). As a correlate of this state of things, the labial cartilages appear to be wholly 

 suppressed in these birds. 



In Strix stridula (Plate XXV. fig. 20) the transpalatine region (tpa) is as well developed 

 as in the Diurnal types ; altogether it has a most instructive skull, and one quite unri- 

 valled for its swollen, spongy lightness of osseous tissue. 



We have, even in this short survey of so small a tract of their structure, seen that the 

 Rapacious birds have much in common, and that the least specialized, as the Cariama, 

 marvellously wedges itself in among the roots of the most specialized of all, even the 

 Palcons and the Owls. 



On the Structure of the Skull in the Laughing- Gull (Gavia ridibunda). 



Several years ago a friend supplied me with a goodly collection of the young of this 

 species, and I took an early opportunity of working them out. 



One of the first things which struck me was the Pluvialine character of these pulli, and 

 this at once struck me as being completely in harmony with resemblances I had noted 

 in these birds to the common Lapwing (Vanellus cristatus). 



I am not sure which side of the boundary between the Plovers and Gulls one elegant 

 type — the Pratincole ( Glareola) — should be placed ; nor whether any man knows the 

 exact proportions of the Plover and of the Tern it contains in its organization. The fact 

 that Gulls are neither " Altrices," proper, nor true " Prsecoces " makes their relation to 

 the Pluvialine types the more instructive ; for the amount of supeif-pluvialine metamor- 

 phosis is not great, although real and measurable. 



* This bone has been lettered in two ways, by mistake ; both mpa and mspg are correct, as a single mesopterygoid 

 becomes a medio-palatine. 



