TO BULLETIN OF THE LABORATORIES 



this process, which descends below the level of the jugal, a nearly ver- 

 tical plate extends upward to form a sliding sheath which clasps the 

 presphenoid and plays back and forward upon it. The flattened ends 

 of the long {.^o) pterygoids are fused with these vertical plates by ex- 

 panded, overlapping plates. There are two curved flanges springing 

 from the point where the pterygoids unite with the palatals. The eth- 

 7710-turbinal plates are more or less ossified and are seen on either side 

 of the rudiment of the vomer. The pterygoids are stout but very 

 unusually long and, on account of the size and position of the quad- 

 rate bones, are quite distant from the basis cranii. Near the point of 

 union of the pterygoid with the quadrate bone, a small hooked process, 

 about . 1 2 long, extends upward from the former bone. What the use 

 or the homologies of these processes may be, we do not know, although 

 they occur in finches and in other birds. 



At the posterior of the two mandiblar processes of the quadrate 

 bone is a bone as large as the head of a large pin, but of irregular 

 shape, which may be regarded as either a sesamoid contributing to lock 

 the jaw or an independent portion of the quadrate. There is also a 

 very minute sesamoid at the union of the quadrato-jugal and the quad- 

 rate. The lower jaw shows no evidence of its composite character. 

 The whole anterior half is enlarged and forms a simple trough of can- 

 cellous bone which may be assumed to consist of the dentary elements 

 of both rami. The surangular, angular and splenial elements of the 

 rami are not distinguishable. The articular portion consists of a huge 

 flange, extending inward and upward and is perforated at the middle of 

 its inner surface for the entrance of Meckel's cartilage. 



What corresponds to the surangular portion is a broad triangular 

 plate extending upward inside the jugal bones and serving to further 

 lock the jaw. Thus, as we have seen, the whole skull is modified in 

 harmony with the enormous rhinencephalic development. 



The hyoid arch is well developed and consists of seven bones, 

 whose homologies, in the present state of our knowledge, cannot be 

 made out. The anterior pair are pointed before and behind and at- 

 tached at the middle to each other and the end of the azygos bone 

 which next follows. The first mentioned bones are called entoglossal, 

 by Gegenbaur, by some American authors, ceratohyals, with no real 

 evidence that they are homologous with the bones so called in other ani- 

 mals. The following element may be called basihyal {^copula of 

 Gegenbauer,) and is flattened to form a vertical plate and bears on 



