116 Trans. Acad. Sci. of St. Louis. 



arate pieces of cartilage in the neighborhood of the processes 

 as shown in Winslow's fig. 16. The same figure shows the 

 dorso-mesal pillar ending caudally at the level of the antorbital 

 process. 



An examination of the larvae of Necturus from 28mm. to 

 49mm. in length has proved that the olfactory lobe as de- 

 scribed by Kingsbury ('95) and the nasal skeleton reach the 

 same level caudally and that the antorbital process is con- 

 nected with the trabecula where this bar is changing from 

 the prismatic shape of the Crista region to the cylin- 

 drical form in the nasal region. The bar of cartilage 

 described by Miss Piatt and Winalow I have found in a 

 28mm. larva lying in the perirhinal membrane of the dorso- 

 mesal side of the nasal sac, opposite the olfactory lobe and 

 dorsad of the olfactory nerve branches. The lattice work of 

 cartilage first described in the adult nasal capsule by Wied- 

 ersheim ('77) arises, as Winslow has it, as processes of the 

 bar and as separate chondrifications. All of these I find to 

 be located in the perirhinal membrane. 



The foregoing facts respecting the origin and relations of 

 the dorso-mesal bar in Necturus recall some of the early con- 

 ditions of the nasal skeleton in Amblystoma and Rana. In 

 the former, an ethmoidal column (Col. eth.) developed inde- 

 pendently in the membranous wall of the olfactory region of 

 the cranium where a cartilaginous wall was wanting, the 

 Crista trabeculae ending caudad of the olfactory bulb. The 

 column lies opposite the olfactory bulb and along the dorso- 

 mesal edge of the nasal sac ; in connection with it there grows 

 a cribriform roof for the sac in its enveloping membrane. The 

 column arches over the olfactory nerve and secondarily joins 

 the trabecula and its crest to complete the olfactory for- 

 amen. In Necturus there is no cartilaginous wall in the olfac- 

 tory region and the Crista trabeculae slopes gradually to end 

 behind the olfactory lobe. A rod of cartilage is developed 

 along the dorso-mesal angle of the nasal sac opposite the olfac- 

 tory lobe in the perirhinal membrane, parallel to the trabe- 

 cula and over the olfactory nerve. From the bar a part of 

 the lattice-like roof of the nasal sac extends. The trabecular 



