46 BULLETIN OF THE LABORATORIES 



PLATE III. 



A series of six transverse sections through the brain of Geomys bursarius, 

 drawn to a uniform scale with the aid of the camera lucida, illustrating the hip- 

 pocampus and tracts of the mesencephalon. The letters have the same value in 

 all figures; a, primary fold of the hippocampus; ch anterior part of chiasm; cop, 

 commissure of the optic lobes;/, descending fornix tract; gu, gyrus uncinatus; 

 ipu, interpeducular nidulus; le, lamina ectalis (superior); It, lamina entalis (infe- 

 rior;) M, Meynert's bundle; n III, nidulus of the third nerve; op, optic tract;///, 

 peduncular nidulus; rxl, radix lateralis olfactoria; sc, superior commissure; III, 

 exit of third nerve. 



Fig. I. Transverse section immediately cephalad of the chiasm. 



Fig. 2 



Fig- 3 

 Fig. 4 



Fig. 5 

 Fig. 6 



Transverse section at the level of the superior commissure. 

 Transverse section through the caudal end of the third ventricle. 

 Transverse section at the region of the mammillary. 

 Transverse section at the level of the third nerve. 

 Transverse section slightly caudad of the last. 



