SKULL OF A HUMAN FETUS OF 40 MM. 339 



foramen, which is limited to the right side, appears just in front 

 of the larger. On the right side the terminal fourth of the upper 

 border of the squama is separated from the slender dorsal tip of 

 the parietal plate by a narrow slit. The parietal plate appears 

 to end freely, but dorsal to this there are what appear to be 

 degenerating cartilaginous cells, connecting the end of the parietal 

 plate with the squama. This may indicate that these structures 

 were united at an earlier time. 



I regret that the dorsal extremity of the head of my embryo 

 is missing, and that I am, on that account, unable to ascertain 

 the condition in this region. On the right side the sections ter- 

 minate in the dorsal occipital prominence, and show that the 

 parietal plate has come to an end before this, as described. Owing 

 to the fact, however, that the sections were cut obliquely, being 

 deeper on the right side than on the left, I am unable to say 

 whether or not the termination of the left parietal plate, and the 

 relations which it bears to the squama, are the same as those 

 found on the right side. I have, however, assumed that they are, 

 and have so constructed my model; this having been done there 

 was only the gap between the dorsal occipital prominences to 

 be filled in, and this I did by reference to the Levi illustrations 

 and Hertwig model. There are indications, on the left side, 

 that the separation of the posterior extremity of the parietal 

 plate will take place, as it has on the right, the cartilage connect- 

 ing it to the squama, in the last few sections, being very thin. 



In the membrane just lateral to the tip of the right parietal 

 plate and dorsal occipital prominence there appears the weakly 

 staining spicule of the interparietal bone. I have not repre- 

 sented it in the model, since only a small fragment is available, 

 the remainder being included in the missing sections. 



The sections go back sufficiently far to show that the occipital 

 squamae unite dorsal to the tip of the superior occipital incisiu-e,- 

 to form the tectunf posterius, thus differing from the findings 

 of Voit ('09) in lepus, who states that the squamae never reach 

 the midline, the edges of the superior occipital incisure being 

 the dorsal borders. I am, of course, unable to ascertain the 

 exact width of the tectum. 



THE AMERICAN JOURNAL OF ANATOMY. VO!,. 16, NO. 3 



