No. 2.] AMPHIUMA MEANS. 399 



bones of the mouth are fully ossified before the nodule is formed. 

 In a specimen eighty-eigJit millimetres long the cells of the dejise 

 connective tissue are concentrically arranged preparatory to the 

 formation of the true cartilage^ which in a specimen ninety niilli- 

 mctres long has made its appearance. The frontal bone, though 

 completely ossified, differs from the adult in the manner of 

 giving exit to the olfactory nerve. Hay implies that Wieders- 

 heim has erred in the following description : " Es handelt sich 

 namlich, wie am besten aus der Figur 20 F ersichtlich ist, um 

 einc an der Unterfiache der vorderen Stirnbeingegend auftre- 

 tende Knochenzwinge, deren mediale Circumferenz vorn und 

 einwarts, und deren laterale mehr nach hinten auswarts gela- 

 gert ist. Beide stehen parallel zum Medianebeine und sind 

 unten gegen die Schadelbasis zu durch eine schmale knocherne 

 Commisur in Verbindung." This description is exactly correct 

 for the adult (Fig. Ill h), biLt in the young tJiere exists only an 

 unmodified aperture in the frontal for the exit of this nerve. 

 Cope (14) attaches great importance to the free margin of the 

 frontal bone in the adult. The frontal in the young has no 

 such margin, the surface being slightly depressed in the middle 

 and regularly convex laterally. 



The frontals overlap the parietals to a considerable extent 

 posteriorly. A cross-section through the posterior part of the 

 parietal of the adult presents the curve of a quarter circum- 

 ference, the depression being external for the temporo-cervical 

 tendon. In the young this bone slopes from the median line 

 outwards at an angle of thirty degrees, and is but slightly 

 depressed in the middle of the distal half. 



The orbito-sphenoid confirms Hay's account, being higher in 

 front than behind. Its ossification is almost complete. The 

 exoccipitals remain almost entirely cartilaginous, being invested 

 with a thin parostosis. The ossification of the condyles is 

 beginning. The pterygoid is represented by a bar of cartilage, 

 free anteriorly but attached to the quadrate posteriorly. The 

 otic capsule is quite surrounded by cartilage. The otolithic 

 deposit is extensive. The prootic is cartilaginous to a con- 

 siderable extent. The stapes shows no evidence of ossifica- 

 tion, as is likewise the case with the columella. The quadrate 



