106 BULLETIN or THE ESSEX INSTITUTE. 



of the nerves coming from the Gasserian ganglion (Fig. 

 18, v). Antero-dorsally the crest gives rise to a rod of 

 irregular shape, which projects forward, outward and 

 downward. This is the lamina cribrosa (e). Below and 

 a little behind this the antorbital process is just beginning 

 to appear upon the side of the trabecula. 



The quadrate is rhomboidal in outline when viewed from 

 the side. It is connected with the trabecular crest by the 

 ascending process, as mentioned above, but as yet it has 

 not fused with the otic capsule. From its posterior angle 

 a slender stapedial process (Fig. 17, sp) extends back- 

 ward into the anterior end of the fenestra ovalis where it 

 joins the small stapes. No pterygoid process is yet 

 developed. Meckel's cartilage articulates with the antero- 

 ventral surface of the quadrate. 



Second STAGE. — (Fig. 19). — In the second stage of 

 the chondrocranium of Amphiuma, ossification is far ad- 

 vanced. The most important additions to the cartilages 

 are seen in the completed nasal capsule and the pterygoid 

 process (pt) of the quadrate which is now developed. 



The distal ends of the occipital processes have devel- 

 oped into a narrow synotic tectum, while the notochord 

 and median portions of the parachordals have disappeared 

 except in the occipital region, where they form a ventral 

 band (p) connecting the two capsules. No changes 

 worthy of notice have taken place in the otic capsules 

 aside from the results of ossification. 



The trabeculse are divided into anterior and posterior 

 portions by ossification in the orbital region. The pos- 

 terior portion remains essentially the same as in the first 

 stage, but the anterior portion is changed by the forma- 

 tion of the nasal capsule. The base of the antorbital 

 process (Fig. 19, anp) marks the posterior end of that 

 portion of the trabecula remaining unossified in front of 



