IOWA ACADEMY OF SCIENCES. 71 



Hay, and by Wilder. A process which may be regarded as 

 a prolongation of the dorsal part of the frontal extends 

 antero-ventrally dorsal to the cartilaginous nasal septum so 

 far as to lie at the side of the posterior part of the bony 

 nasal septum (premaxilla). The portion of the process 

 immediately posterior to the bony nasal septum meets in 

 the middle line the corresponding process of the opposite 

 side ventral to the dorsal process of the premaxilla. This, 

 the posterior part of the dorsal process of the frontal, 

 forms the dorsal and median wall of the olfactory open- 

 ing, the ventral and external wall of the latter is formed 

 by the border of the second part of the frontal above 

 described. In later stages the antero-dorsal process appar- 

 ently fuses with the ventral sheet near the middle line, 

 thus forming a complete ring of bone around the olfactory 

 opening. At this stage, however, the ring is incomplete on 

 the median side. Hay seems to question the accuracy of 

 the statement of Wiedersheim that in the adult the ante- 

 rior part of the frontal forms a canal in which lies the 

 olfactory nerve as it passes into the nasal capsule, but a 

 careful examination of an adult skull can hardly fail to 

 confirm Wiedersheim's statement. In my specimen the 

 olfactory opening has not as yet assumed a canal-like form. 



The parasphenoid has approximately the relations of 

 the adult condition. Anteriorly, the pointed portion lying 

 between the two vomers has a groove on its ventral sur- 

 face, and in this groove is the posterior part of the pala- 

 tine process of the premaxilla. Toward the tip of the 

 parasphenoid the groove breaks completely through the 

 bone so that the latter is forked and ends in two delicate 

 processes, each closely wedged in between the vomer of its 

 respective side, and the palatine process of the premaxilla. 

 The extreme posterior tip of the latter is so coalesced with 

 the parasphenoid that no line of demarcation can be dis- 

 cerned in the sections. 



The parietals do not meet in the middle line except near 

 their posterior ends. Laterally each sends a process over 

 the ear capsule nearly to the^'^squamosum. Antero-later- 

 ally each overlaps the orbito-sphenoid cartilage. Poste- 



