214 SiiUFELDT on the Osteology of Cluclus Mexlcanus. 



pressing as many of the technicalities in terms, as is compatible 

 with exactness, and in accord with the tastes of those who have 

 not devoted themselves especially to anatomical reading and 

 work. 



In studying the skeletons of birds, or of anything else for that 

 matter, the student must keep the fact ever present in his mind, 

 that the great value of such studies and the descriptions that may 

 follow them, rests almost entirely upon the compai'isons that he 

 makes ; the more carefully and minvitely he compares the form he 

 may have under consideration with nearly related forms, the 

 greater will be the value of his results ; to this end tend all the 

 studies of biologists of the present day. 



WitJi respect to the skull of Cinclus^ our space will not per- 

 mit us to enter upon the engaging part of the subject as to the 

 mode of formation of this part of the skeleton in the adult 

 from the many segments found in the cranium of the chick, it 

 being enough for us to say that the usual bones ossify, unite, and 

 leave the ordinary ones free, as the pterygoids, the ossa quadrata, 

 and the lower jaw. The superior mandible is drawn out into a 

 sharp point, and the bony nostril on either side occupies con- 

 siderable space, being long and elliptical in outline ; as in all 

 nearly related genei'a these apertures are not separated by a bony 

 partition or septum, but below we detect a delicate vomer in the 

 median plane. 



The eye-cavities or orbits are well shut oti' from the nasal 

 chambers beyond them by broad bony walls composed of the 

 usual elements, and here each is of a quadrate figure, as seen in 

 so many genera of birds. The upper and outer angles of these 

 osseous partitions are rounded. The almost complete separation 

 existing between the two cavities just referred to by no means 

 exists between the orbits themselves, for here we find an extreme- 

 ly deficient septum, and a large aperture leading into the brain- 

 case at the usual site of the exit of the nasal nerves, the openings 

 for the optic nerves being circular and entire. 



On the inferior aspect of the skull we find maxillo-palatines, 

 of a more or less spongy composition, existing between maxilla- 

 ries and the delicate palatines, which latter are slightly bent down- 

 wards from the horizontal plane. The pterygoids are very 

 slender, and articulate in the usual manner with the quadrates 

 and the palatines. 



