CENTRAL NERVOUS SYSTEM OF ARMADILLO. 287 



depressed, quadrilateral area immediately anterior to the optic 

 chiasma. 



The cerebral hemispheres (PI. XXIV., Figs. 2 and 4) show as 

 high a development as any of the armadillos figured by Smith. 

 The short anterior rhiual fissure (PI. XXIV., Fig. 4, Fis. R/i. A.] 

 begins in the boundary between the bulbus olfactorius and the 

 hemispheres. It extends obliquely upwards for about a fourth 

 of the length of the hemispheres. The posterior rJiiiial fissure 

 (PL XXIV., Fig. 4, Fis. Rli. P.] begins near the posterior border 

 of the hemispheres and runs horizontally towards the anterior 

 part of the hemispheres, where it joins the sulcus fi (PI. XXIV., 

 Fig. 4, ,-t). In the most dorsal part of the hemispheres, the sulci 

 f and o (PI. XXIV., Fig. 4) are faintly developed. The latter of 

 these two sulci corresponds to the suprasylvian sulcus of other 

 mammals. On the mesial surface of the two hemispheres the 

 sulcus limitans pallii (PI. XXIV., Fig. 3, Sul. L.] is found. 



In this animal, as in all mammals, a series of nerve fibers, or 

 commissures, serve to connect homologous areas of the two 

 hemispheres. 



The most dorsally placed commissure is in the form of an in- 

 verted, obliquely placed U (PI. XXIV., Fig. 3, Cor. Col.). The 

 arms of the U are formed by the corpus callosum (PI. XXIV., 

 Fig. 3, Cor. Cal.\ and the ventral and dorsal psalterium (PI. 

 XXIV., Fig. 3, Psal. V. and D.}. The curve of the U is formed 

 by the splenium (PI. XXIV., Fig. 3, Sp/.}. This commissure is 

 placed more nearly vertical, and is rather smaller than in most of 

 the edentate brains figured by Smith. There is really no apparent 

 distinction between the dorsal and ventral psalterium. The psal- 

 terium is slightly longer than the corpus callosum. The two arms 

 of this dorsal commissure are in contact with each other for the 

 greater part of their extent, only the most ventral part of the psal- 

 terium extends a little further ventrally than the corpus callosum. 

 The interval between the two arms of the dorsal commissure is 

 called the septum lucidum in human anatomy. In the edentates, 

 Smith calls this the paracommissural body. But since the two 

 arms of the commissure are in contact with each other for the 

 greater part of their extent, there is practically no septum lucidum 

 or paracommissural body, in this armadillo. 



