AND DEVELOPMENT OF THE BIRD'S SKULL. 149 



The occipito-otic region is now one large shell of hone (Plate XXVII. figs. 7-10) ; in 

 the hind region (fig. 10) the " lateral occipital fontanelles " (lof) are still open. 



The basitemporal plate (fig. 9, bt) has now obtained its perfect form ; it is subtriangular, 

 bnt the sides are convex, and the base is emarginate, and it has ear-like processes at 

 its angles ; these help to floor in the tympanic cavity. Prom the parasjmenoidal rostrum 

 {pas) the basipterygoids have disappeared, so that the Pluvialine stage has been passed 

 in this part of the skull. 



All the elements of the face are very slender and elastic, both those of the outer and 

 also those of the inner series. The great perpendicular ethmoid (pe) has reached the 

 "notch" in front and above, and has nearly met the basisphenoid behind and below. 

 There are still large postorbital and a large interorbital fenestra (pof, iof). 



The nasal cartilages (the fore part of which had been removed in the specimen figured) 

 are all cartilaginous, with the exception of the back wall or pars plana (pp), which 

 is made bony by a centre of its own. 



Outside this there is an anvil-shaped lacrymal, Pluvialine in form, but answering to 

 that of the larger types; its lower crus rests upon the outstretched antorbital plate 

 (Plate XXIV. fig. 7, I, pp). The upper turbinal coil (aliethmoid) divides the groove for 

 the olfactory nerve from that for the trabecular or naso-orbital. 



The nasal processes of the premaxillaries were laid upon and wedged in between the 

 upper plate of the nasals (npx, n). The upper plate of the nasals lies upon and is wedged 

 in between the frontals (n,f). The frontals are sinuously applied, behind, to the fore 

 margin of the parietals (f,p) ; this harmony -suture is the " coronal " of human anatomy. 

 A " sagittal suture " runs along the whole skull and face, from the fore end of the nasal 

 fossa, where the premaxillaries are soldered together, up to the notch in the upper surface 

 of the superoccipital (fig. 10, so), the remains of the divisional line of its two primary 

 halves. 



The falcate squamosal (sq) elegantly binds the whole cranial cavity together on each 

 side ; it runs upwards and downwards obliquely, behind, lying like a tile over the slant- 

 ing occipital edge. 



The nasals, as is the wont of the Pluvialine types, are sharply split into two crura 

 (figs. 7 & 8, n). These run forwards, tying down the upper and lower branches of the 

 premaxillaries (n, npx, dpx). 



The pterygoids (pg) are long, slender, and inbent. They are pedate behind, having 

 an epipterygoid process, with an oval hollow above ; and the proper end of the bone has 

 an acetabular facet ; both these embrace similar convexities on the fore margin of the 

 quadrate (q). 



In front the pterygoid, having lost its mesopterygoid spike, which is now part of the 

 palatine, fits, by a short tooth, into a shallow socket in the end of the palatine (pa). In 

 front, the palatine is a long, slender needle of bone, which is now tied to, and afterwards 

 anchyloses with, similar needles, namely, the fore part of the maxillary (mx) and the 

 palatal process of the premaxillary (ppx). 



The outer edge of the two-keeled hinder part of the palatine has no more outgrowth 

 as a proper transpalatine portion than the Plovers. (See my " Gallinaceous Birds and 



x2 



