294 MR. W. A. FORBES ON THE GREAT ANTEATER. [Mar. 7, 



above by a shallow fissure (a), which, at the level of the anterior 

 extreniityoftheproiniuent"hippocanipallobe," turns downwards, and 

 runs along the external and interior face of that lobe till it terminates 

 on its inner face (fig. 4, a), not, however, reaching the hippocampal 

 sulcus (h). At the point where its downward course commences 

 there is a small triangular area (l. s.s.) exposed on the lateral surface 

 of the brain, from which a short curved shallow sulcus (s) runs a 

 short way upwards, forming with the descending part of a a forwardly- 

 convex curve. In the larger specimen figured (fig. 3) this short 

 upwardly-running sulcus («) is separated, as will be seen, by a narrow 

 bridging fold from the triangular depression and its posterior continu- 

 ation (a). From the antero-inferior angle of this triangular space, 

 but separated by a very narrow, more or less deep, bridging convolu- 

 tion from a, another sinuous fissure (6) runs forwards and upwards 

 to terminate near the anterior angle of the hemisphere ^ Above, 

 on the supero-lateral aspect of the brain, and nearly parallel with 

 the median longitudinal fissure, is a distinct longitudinal sulcus (c), 

 convex upwards, which runs in an autero-posterior direction for a 

 space of r2 inch. 



Finally, parallel with the posterior edge of the hemisphere, dividing 

 the external surface of this "temporal lobe," is a vertically-directed 

 sulcus (d) about '/S inch in extent. 



On the internal aspect of the brain (fig. 4) runs a well-marked 

 " calloso-marginal " sulcus (cm), broken up into three or more 

 parts, the most posterior being nearly vertical in position, and sepa- 

 rated by but a little space from the posterior extremity of fi.ssure a. 

 In its usual position is a well-marked hippocampal sulcus (A), with 

 abroad "fascia dentata'^ between it and the corpus fimhriatum, 

 \\\e fascia dentuta being continued, as described by Prof. Turner in 

 Basypus ^ as a thin layer of longitudinally-disposed fibres over the 

 corpiis callosvm to near its ffenu. The hippocampal sulcus does not 

 extend as high as the corpus callosum. The lateral ventricle is fair- 

 sized : I can see not a trace ot any posterior cornu. The hippocamjnis 

 major is strongly convex. The " hippocampal lobe " has, on its 

 interior aspect, a few irregular dentations developed near its autero- 

 internal angle. 



In the smaller and simpler hv?im o^ Tamandua (represented dia- 

 grammatically in fig. 5, p. 295), the only sulci present are those 

 corresponding to a, b, c in the larger species, with some slight repre- 

 sentatives of d. 



Adopting the late Prof. Broca's ideas ^ as to the nature and com- 

 position of the " scissure limliqve," the inferior arc of this is clearly 

 represented by the fissure a, which is separated by a narrow " pli de 

 passage retro-limbique" (fig. 4, r.l) from its superior arc, represented 



' In the smaller specimen (fig. 2), this fissure is, on the right-hand side only, 

 broken up into two bv a narrow bridging convolution (-f-). 



2 Journ. Anat. Phj's. i. p. 314 (18G7). 



^ " Anatomic comparee des circonTolutions cerfibrales. Le grand lobe lim- 

 bique et la scissure limbique dans la strie des Maminileres," Revue d'Anthro- 

 pologie, vii. pp. 385-498. 



