MOKPllOLOGY OF TUE BRAIN IX THE MAMMALIA. 337 



Platau and Jacobsolm in the brain of Lemur rariiis : nov have I ever found the sulcus 

 labelled "Nebenfurche " (Taf. 3. fig. 2, 2) in the l)raiii of any Leinur. 



In the brain of Lemur fnlvus the diagonal sulcus is genei-ally well-developed and often 

 deeply notches the supraorbital margin. 



The lateral and coronal sulci approach much more closely than is the case in the 

 other species, and in some instances they even seem to join. Tlius Beddard says (Proc. 

 Zool. Soc. 1895, p. 113) : — " In the brain of Lemur monyoz the angular [lateral ' and infero- 

 frontal [coronal] sulci are completely continuous.'' But even if this sometimes happens, 

 it is by no means the usual condition in L. fnlcus. Por, as the same writer remarks 

 (p. 113), this does not occur in L alblfrous, nor iu L. iiigrifroi/s nor L. (uijuaneiisis, all of 

 Avhicli may be included in the s-pecmsfulviis. ^Vithin this si)ecies all varieties of the upp(>r 

 ends of tlie supra- and postsylvian sulci are found. Sometimes a long arcuate sulcus d 

 is fused at one end to the suprasylvian sulcus and almost joins the postsylvian at the 

 other. Not infrequently the sulcus d is joined to the postsylvian and not to the supra- 

 sylvian ; but in some cases it remains independent of botli, ;is in tlie .-^pecies rari/is. 



In most cases the caudal end of the lateral sulcus behaves as it does iu the species 

 macaco, and not as in rarius. 



In the two specimens of Lemur ca/la which I examiiu'd thei'c was nothing distiuetivc 

 and they might well have belonged to the species fulrus. 



The skull of Lemur rubrivetiter, Geoff., exhibits ridges corresponding to typical supra- 

 sylvian, postsylvian, lateral, postlateral, coronal, orbital, aud diagonal sulci, witii nothing 

 indicative of a distinct specific type. 



Tlie large brain of the extinct Leinur Julli/i [Pahechirogaleus JuUtji, G. Grand.) 

 exhibits the tyj^ical Lemurid plan of sulci with diagrammatic clearness. 



The suprasylvian sulcus with a long deejily-incised inferior exposed limb, the shallowei- 

 furrow indicatijig the pscudosylvian sulcus ; simple, long, linear orbital and diagonal 

 sulci; lateral and coronal sulci which almost (if not quite) meet as \\\ Lemur f ulcus; 

 and a .small sulcus f, all conform to the most typical Lemurid pattern. 



The or])ital sulcus presents none of the irregularity which it has ao-quiivd iu most of 

 the recent Lemurs. 



The Cerebr.\l Hemisphere in the Genus Hapalemuk. 



An examination of tiie ridges on the interior of tlie ci-aiiial cavity of Ilapalemur 

 reveals a pattern of sulci which does not appreciably differ from that exliibited in tlic 

 genus Lemur. Tlie typical Sylvian fissure, a sliort lateral sulcus, a long coronal sulcus, 

 and a typical linear orbital sulcus are present. 



Milne-Edwards has pu])lished illustrations of a brain of Ilapalemur simus * which 

 presents similar features. Beddard has described three brains belonging to this genus, 

 two of the species griseus and one of the species simus ■f. The hemispheres of the 

 smaller specimen of the former species were 33 mm. long and 2G mm. broad, the larger 



'Histoire de Madiiga.scar,' (2) tome vi. pi. 122*. figs. 1. 2, '.i, 4, and .3. 

 Proc. Zool. Soc. lyul, pp. 127 & 12S ; also I'iol'. Zool. Soc. 18!)1, p. 4.J7. 



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