1 876. J ANATOMY OF CHAUNA DERBIANA. 197 



Screamer more closelv approaches. It evidently does not share the 

 peculiarities of the former, in all species of which the surface of 

 origin for the pair of large extensor muscles of the mandible is 

 characteristically compressed from side to side, and elongated from 

 above downwards, at the same time that there is the pair of openings 

 above the foramen magnum (figs. 1, 2, 3, p. 198). 



Again, from a comparison of the inferior surfaces of the same three 

 skulls, it is equally evident that in the Screamer the prsemaxillse, 

 mamillaries, and dentaries agree with the same bones in the Gallina- 

 ceous bird in not being large and outspreading. The palate of Chauna 

 is represented in fig. 4. 



In the Screamers the skull is, no doubt, as in the Anseres, desmo- 

 guathous, having the maxillo-palatines united across the middle line ; 

 but this character is not sufficiently important, to compel us to unite 

 the two groups ; for if such were the case it would be necessary to 

 give credence to an association of birds which is in other respects 

 extremely unnatural. In the Capitonidee, for instance, Megalcema is 

 not desmognathous, whilst Tetragonops is so. 



As before stated, in the Anserine birds the lachrymal region is 

 specially long. This is least marked in the Cereopsis Goose (Cere- 

 apsis novce-hollandice), where, however, it is clearly apparent. In 

 Chauna, the lachrymal region is as short as in the Gallinse, not in 

 the least elongated. 



In both the Anseres and Galling the pterygoid bones have large 

 faceted surfaces for articulation with the basisphenoid rostrum. In 

 both groups these facets .are situated very far forwards — quite at the 

 anterior ends of the bones in the latter ; in Chauna, however, these 

 articulations are quite independent of the anterior ends of the bones 

 (fig. 1), being nearly as far backward as the middle of their otherwise 

 tree moieties. 



As to the quadrate bones, their cranial articulations are bifid, 

 which is the case in all birds except Struthio, Rhea, Dromceus, 

 Casuafius, Apteryx, the Crypturi, and some (most) of the Gallinae. 

 They do to a certain extent resemble the same bones in the Anseres 

 in having the articular surfaces for the jugal arches situated some 

 way behind the level of their mandibular articulations (not a Galli- 

 naceous character), which latter they also resemble in configuration, 

 the usually extended outer facet not running backwards and inwards 

 as in most birds but not in the Gallinse. 



In the Gallinse, as in the Crypturi, the pterygo-qnadrate articula- 

 tion is much longer than in other members of the class. In Chauna 

 this is not the case. 



In Chauna the angle of the mandible is much prolonged and up- 

 curved, as in the Anseres, from which it however differs in not being 

 deeply excavated in the interval between the upturned process and 

 the inwardly-directed articular angle. It must be remembered that 

 the mandible is much the same in the Gallinee. 



It must also be remembered that the Screamers are the only 

 birds in which there are no uncinate processes to the ribs, as has been 

 jjhow/n by Mr. Parker. 



