THE CHONDROCRANIUM IN THE ICHTHYOPSIDA. 107 



the optic foramen. A narrow column of the trabecular 

 crest projects upwards from just in front of the base of the 

 antorbital process, and upon the anterior end of the eth- 

 moid plate a thin nasal septum is developed. Two carti- 

 lages upon each side arise from the dorsal end of the 

 septum. From its posterior end a cylindrical rod, the tectal 

 cartilage ((e) extends backward and outward to the dorsal 

 point of the remnant of the trabecular crest. From the 

 posterior end of the septum a band of cartilage extends 

 forward and expands into a broad sheet, the nasal tectum, 

 roofing over the whole anterior portion of the olfactory 

 organ. Where the nasal duct passes out to the exterior 

 (nl) at the anterior end of the tectum, a complete ring of 

 cartilage encircles it. Laterally the nasal roof is con- 

 nected by a band curved ventrally with the cornu (c) of 

 the trabecula. And from the postero-lateral margin of 

 the tectum a flattened rod (?) passes backward to the tec- 

 tal cartilage, fusing with it at a point just above the an- 

 terior end of the antorbital process. 



While it is impossible to homologize all the parts of the 

 nasal capsule of Amphiuma with those in Amblystoma 

 there are some points in which the similarity between them 

 is very close. The septa, ethmoid plates, and tectal car- 

 tilages are essentially alike in both. The lamina cribrosa 

 and dorsal process of Amblystoma are represented in Am- 

 phiuma by the rod connecting the tectal cartilage with the 

 nasal tectum. The open anterior end of the capsule of Am- 

 phiuma is quite different from the cup-like end of Ambly- 

 stoma to which it must be compared. This difference in 

 the capsules is, of course, correlated with the relative 

 change of position of the nostrils, which are at the ante- 

 rior end of the capsules in Amphiuma and in the middle 

 of the sides of the capsules in Amblystoma. In Amphi- 



