AND DEVELOPMENT OF THE BIRD'S SKULL. 125 



ossicle, which lies between the ethmo-palatine hooks (fig. 9, v a , epa) ; this is a minute 

 posterior vomer, this element being double, as in Scythrops and other " CuculinEe." 



Caprimulgus is very passerine in having a huge double (symmetrical) vomer (Plate 

 XXII. fig. 1, v) ; but Steatornis comes much nearer Podargus, and has an azygous vomer, 

 of a clubbed shape in front, articulating with the palatine commissure. But the flat 

 anterior foot of the Chelonian vomer is again, as in Podargus, represented by a small 

 bony wedge in the cleft behind the maxillo-palatine synostosis. 



The elegant leafy palatine arch is as fraught with interest as any other part of this 

 bird. The long prepalatine bar is aborted (compare Plate XXI. fig. 8, prpa, with 

 Plate XXIII. fig. 6, prpa) ; the broad truncated ends of these, the shortest of ornithic 

 palatines, are joined to the great fore jaw by a half-ankylosed dentate suture. Eor 

 short distance they are distinct, but they soon converge ; these interpalatine plates are 

 ankylosed together, and form a bony raphe below to this superaddition to the bird's 

 hard palate. This line of union is half the length of the palatines ; a rounded notch 

 separates the extreme ends of the bars. The transpalatine process is triangular, with a 

 rounded point ; it is not one third the relative size of this part in Caprimulgus ; in 

 Steatornis it is entirely gone, as in many Cuculines. In that intermediate Goat- 

 sucker the interpalatine processes are rounded lobes, that grow near to each other in a 

 horizontal manner, but do not meet ; whilst in Caprimulgus (Plate XXI. fig. 8, ipd) the 

 interpalatine ridges run parallel a long way, a short distance apart, and end in a delicate 

 spur. In Steatornis the ethmo-palatal commissure shows no medio-palatal keystone as 

 in Caprimulgus (Plate XXI. fig. 9, mpa) ; but in Podargus, although this tract is very 

 short, only half the extent of the lower hard floor, yet here, again, we have the two 

 azygous medio-palatines, the undoubted symmorphs of those I have described in the 

 Pern-Owl (Plate XXI. fig. 9, mpa, and Plate XXIII. fig. 8, mpa). In Steatornis the 

 palatine commissure is longer than in either the Giant or the Common Goatsucker, more 

 like that of Scythrops (Plate XXIII. fig. 1, ipa) ; the posterior notch is similarly small. 



In all these thin types the apex of the palatine arch, or epipterygoid, is aborted, and in 

 Podargus and Caprimulgus this bone is very spongy (Plate XXIII. figs. 6 & 7, pg, 

 and Plate XXI. fig. 8, pg) ; in Steatornis it is less spongy and more crested. In this 

 latter bird the facet for the basipterygoid has an overlapping process, by which it lies 

 over as well as against the basal facet ; in Caprimidgus there is a slight rudiment 

 of this structure; in Podargus there is no joint at this part. All these three types 

 agree in being embryonic, as regards the mesopterygoid. This spur does not segment 

 off in either; in the old Pern-Owl it has become aborted; the young agrees with 

 Steatornis and Podargus (Plate XXI. fig. 11, and Plate XXIII. fig. 7, pg) ; it lies in a 

 depression and is strongly bound to the supero-median surface of the palatine. I find 

 no defined os uncinatum in either the Pern-Owl or Podargus ; but in Steatornis it is as 

 well developed as in Scythrops (Plate XXIII. fig. 1, ou), and has two cartilaginous tapes 

 that tie it in front and behind. 



The lacrymal is large in the Pern-Owl (Plate XXI. fig. 8, I) ; in Podargus it seems to 

 be absent ; but a small ossicle may have coalesced with the supero-external angle of the 

 nasals, in front of the narrow frontals, as is the case with a larger piece in Steatornis. 



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