70 IOWA ACADEMY OF SCIENCES, 



shows no connection with the nasal cartilages except 

 throu|?h the connective tissue that in this region binds 

 together premaxilla, vomers and nasal cartilages. Wieder- 

 sheim says that in the adult the anterior ends of the 

 vomers come in contact in the middle line just posterior to 

 this isolated unpaired cartilage. In a dry preparation of 

 an adult skull I find a postero-ventrally directed cc'-iiical 

 bony process of the premaxilla slightly overlapping and 

 w^edged in between the anterior ends of the vomers. This 

 is in the position occupied by the isolated cartilage in 

 question in my young specimen and in the adult condition 

 as described by Wiedersheim and Hay. I do not find the 

 bony process in the young specimen. 



The vomers (vermero-palatines) require little mention 

 beyond that of the preceding paragraph. 



The maxillae and the prefrontals have essentially the 

 adult relations. Along the border of the maxilla are 

 numerous teeth, of which only three are as yet consoli- 

 dated with the maxilla. 



The frontals at this stage do not meet in the middle 

 line, except at the peculiarly modified anterior portion 

 underlying the dorsal process of the premaxilla. The 

 frontal consists of two portions. There is an external 

 part roofing in the anterior brain cavity of its respective 

 side. Posteriorly this portion overlaps the parietal, and 

 antero-laterally rests on the anterior prolongation of the 

 trabecula, known as the tectal cartilage. A second por- 

 tion of the frontal is, at this stage, a thin sheet extending 

 antero-ventrally from the anterior border of the dorsal 

 part of the bone, mesial to the tectal cartilage as far as the 

 ethmoidal basal plate and nearly to the middle line, form- 

 ing the chief part of the anterior wall of the brain cavity 

 and closing the greater part of the large opening between 

 the dorsal tectal cartilage and the ventral trabecula. At 

 this stage this part of the frontal is imperfectly ossified 

 and its exact limits are hard to define. At its dorso- 

 median border is the olfactory opening into the nasal cap- 

 sule. The peculiar structure of the anterior end of the 

 frontal has been noticed and figured by Wiedersheim, by 



