200 PEOF. W. K. PAEKEE ON THE MOEPHOLOGT 



instead of the pterygoid process of cartilage growing rapidly at first, and then, during 

 metamorphosis, becoming less and less, it comes late, grows slowly, and then does not 

 diminish in size. 



This is a correlate of the curious abortion of the bony pterygoid which usually seizes 

 upon the cartilage, converting it into its own substance. This outgrowth of cartilage 

 is falcate, with the convex margin inwards, and the point looking towards the point of 

 the short zygomatic process of the maxillary. 



The large pterygo-palatine bone is now reduced to two remnants, one in front and one 

 behind ; three fourths of it has been absorbed. The pterygoid piece (behind c.pg) is an 

 irregularly five-sided plate, applied to the inner face of the suspensorium in front and 

 below; it does not project forwards, but its edge there is concave; above it is only half 

 the width of the quadrate. 



The foremost patches of teeth have crept off the vomers (v) on to the palatines, just 

 where these bones have coalesced, so that the exposed part of the vomer is edentulous. 

 Each palatine bone (pa) is mainly directed transversely ; it extends outwards much 

 further than the hinder process of the vomer, to enclose the inner nostril (i.n), and some- 

 what underlies the more extended ethmo-palatine cartilage (e.pa). Towards the mid 

 line it is curved backwards, lies beneath the parasphenoid (pa.s), has its concave facet 

 scooped, and soon ends in jagged projections. 



Below, close behind the vomer, where the bone is the thickest, there is a row of sharp 

 decurved teeth, arranged in sigmoid manner. The greatest arch in this series is between 

 the internal nostril and the mid line of the skull; turning backwards, the right and left 

 rows nearly meet. Although the palatine bones go no further backwards, the tooth- 

 tracts do ; they are continued so far back as to end opposite the foramen for the facial 

 nerve (7). At first in a single row, and almost close together, they gradually widen their 

 plot until there are five or six teeth in one transverse line ; the interspace along the 

 middle of the parasphenoid also gently widens. 



These lanceolate tracts, with their out-turned sigmoid fore end, are very elegant ; they 

 are the so-called sphenoidal teeth. These rasp-like tracts existed before the palatine 

 bones were formed, and grow far backwards, independently of them, where the bone has 

 been absorbed. 



The vomers (fig. 2, v) are some distance apart, except behind, where they unite with 

 the palatines. Together they form a deeply notched fan, and each leafy plate has a 

 deep rounded notch on each hinder margin for the internal nostril {i.n). Their interior 

 margin is ragged, and their very large palatal development causes the palatine plates of 

 the premaxillaries and maxillaries (px, mx) to be narrow. Reference to the figures of 

 the last stage (PI. XX. figs. 5, 6, v) shows how strangely these bones have altered from 

 their larval form. 



The premaxillary (px) is scarcely less transformed : looking at the bone in the three 

 larvae, we see it formed of a gently arcuate dentigerous part in front, and of two long, 

 lanceolate nasal processes that run back and lie over the frontals ; the middle nasal 

 passage (m.n.p) is seen between the roots of these crura and the internasal carti- 

 lage (i.n.c). 



