BY J. T. WILSON. 135 



exceeding 2 ram. The height does not diminish until the hinder 

 end of the ])alatine plate of the bone is reached. Here, however, 

 the vertical portion of the hone is continued backwards dorsally 

 for a considerable distance behind the plane of the posterior end 

 of the horizontal palatine plate, in the form of a thick bony 

 spur (e), still grooved dorsally for the septum, and gradually 

 undergoing reduction in height at the expense of its ventral border, 

 which becomes elevated more and more dorsally above the 

 horizontal plane of the palate. This spur finally terminates in a 

 jjosterior bifurcated extremity. The forks (morphologically con- 

 tinuous with the dorsal alar laminse of the vertical portion of the 

 bone in front) are in contact with the lips of the ventral border 

 of the cartilaginous nasal septum, and they are in continuity 

 posteriorly with the fibres of strong bilateral " vomerine " 

 ligamentous bauds of similar sectional area to themselves which 

 connect them with the corresponding forks of the bifid anterior 

 extremity of the vomer. In the dissected specimen from which 

 this description is chiefly taken, the distance between the extreme 

 tips of the forks of the vomer and those of the spur of the dumb- 

 V)ell boue is about 2 mm., and the latter projects backwards beyond 

 the plane of the posterior extremity of the palatine plate of the 

 dumb-bell for a distance of 4 mm. Now the posterior extremity 

 of the latter bony plate is only about 0-5 mm. in front of the 

 anterior end of the maxillary palate, to which it is usually regarded 

 as articulated ; and accordingly the jiostaxially directed spur of 

 the dumb-bell bone lies in a horizontal plane above (dorsad of) the 

 maxillary palate, from which indeed it is separated near its hinder 

 end by a vertical distance of about 1-5-2 mm., as is also the bitid 

 anterior end of the vomer and the "vomerine ligament" aforesaid. 

 This interval, spanned by the series of structures just mentioned, 

 is not filled up by any septal structure whatever, but in the 

 living or recent specimen forms a low antero-posteriorly elongated 

 aperture of communication between the two nasal fossae which is 

 lined by columnar epithelium similar to that lining the adjacent 

 parts of the nasal fosses (c/. fig. 4 i). The maximum height of 

 this internasal aperture is about 1 mm., while its length antero- 



