22 ALLIS. [VOL. I. 



the anterior end of the anterior semicircular canal, and forms 

 the anterior boundary of the labyrinth recess, thus occupying 

 exactly the place assigned by Thane to the prootic in man, 

 and by Parker to the same bone in fishes. It adjoins ante- 

 riorly the hind edge of the alisphenoid, as it should ; it lies 

 inferior to the anterior end of the squamosal, as it also should; 

 and it is the only primary bone of the skull of Amia that has 

 any direct relation whatever to the spiracular canal, the homo- 

 logue, according to Wright (No. 35, pp. 479, 488, 492), of 

 the canalis tubo-tympanicus of higher vertebrates, from which 

 the Eustachian tube develops. 



The sphenotic nuclei of the sphenoid bone of man are said 

 by Sutton (No. 29, p. 580) to arise, after the appearance of 

 the alisphenoidal and basisphenoidal nuclei, as " earthy spots 

 in the lingulae," and they alone of all the nuclei of the bone 

 are so specifically characterized by him. According to Thane 

 (No. 24, vol. ii, pt. i, p. 76) they form not only the lingulae, 

 but also the adjoining parts of the carotid grooves. The 

 corresponding regions in the skull of Amia and teleosts are 

 occupied by the parasphenoid. My work accordingly leads 

 me to accept Huxley's and Parker's conclusions that " the basi- 

 temporal rudiments of the parasphenoid ' of Sauropsida 

 are the homologues of the lingulae of man (quoted No. 29, 

 p. 584), rather than Sutton's conclusion that the homologues 

 of the latter bones are found in the sphenotics not only of 

 Sauropsida, but also of fishes (No. 29, p. 585). 



The postorbital ossification of Amia and other fishes, al- 

 though universally called either the postfrontal or the sphenotic, 

 must not be confounded with the postfrontal bone of Reptilia, 

 which is; according to Parker (No. 20, p. 96) and Brooks (No. 

 8, p. 171), simply a membrane bone, the homologue doubtless 

 of the postfrontal bone of my descriptions of Amia, or of that 

 bone and one or more of the postorbital bones combined. 

 The reptilian postfrontal is said by Bardeleben (No. 4) to 

 be represented in man by the suprasquamosal or epipteric 

 bone. 



But one bone now remains to be considered, - - the basi- 

 sphenoid. 



