4y 



and several other forms. Before eutering the fissure separating the 

 two great divisions of the olfactory nerve, it branches unequally. The 

 smaller bundle joins the fila olfactoria on the median side, while the 

 main branch, which in reality is very slender, passes downward in the 

 fissure, and then obliquely outward along the base of the olfactory 

 cup as in Squalus acanthias. Its particular points of union with the 

 olfactory cup and its distribution within have not yet been traced. 



In Spin ax nig er. — The brain in this relatively small form is 

 similar to that of Squalus and Centrophorus. The median furrow is 

 more shallow and the dorsal elevation of the prosencephalon does not 

 extend so far forward. The new nerve is slender and difficult to 

 dissect free from the membranes. Its point of connection with the 

 brain is more dorsal than ventral. In passing to the tractus it lies 

 closely applied to the anterior surface of the prosencephalon. It then 

 passes in a direct line over the bulbus to the median fissure in which 

 it disappears. It has a small ganglion near the base of the bulbus. 

 The nerve branches in 

 front of the ganglon, one 

 part going to the median 

 and one to the lateral 

 division of the olfactory 

 nerve. 



In Scy mnus lichia. 

 — I have had a single 

 specimen of this archaeic 

 form. The brain is elon- 

 gated and similar to that 

 of Heptanchus (cf. Fig. 11). 

 The new nerve is very 

 slender ; its roots lie deep 

 within the median furrow 

 of the prosencephalon. In 

 front, it passes in almost 

 a direct line to the bulbus 

 and dips into the fissure 

 between the median and 

 lateral divisions of the 

 olfactory nerve. 



InSquatinaangelus. — The brain of Squatina (Fig. 14) presents 

 a very graceful outline. The olfactory cup and bulbus are relatively 

 large, but the olfactory tractus is very slender. The new nerve is 



Anat. Anz. XXVI. Aufsätze. 4 



Fig. 14. 

 nat. size. 



Brain of Squatina angelus, from above, 



