334 PEOF. G. ELLIOT SMITII OX THE 



l)y the name "lateral." The auterior extremity of this sulcus always bends laterally, so 

 as to be approximately parallel to the upper part of the suprasylvian sulcus (fig. 1). Its 

 posterior extremity usually becomes bent in a mesial direction. It often happens, 

 hoAvever, that this mesially directed limb remains as a transverse sulcus widely 

 separated from the sulcus lateralis (fig. 3). It may be distinguished as the postlateral 

 sulcus. 



Behind and parallel to the suprasj'-lvian and pseudosylvian sulci there is a sulcus of 

 varying length and depth, which may be distinguished as postsylvian. 



The mode of termination of the supra- and postsylvian sulci is exceedingly variable 

 (compare figs. 1, 2, 3, G, and 7). In many cases the upper extremity of the supra- 

 svlvian sulcus bends backward so as to almost reach the postsylvian (fig. 6) : in 

 other cases (tig. 7) the latter curves forward to approach the suprasylvian ; and 

 in other cases again (fig. 3) the intercalated furrow is separated from both sulci. 

 We may distinguish it by the letter d, and defer the discussion of its significance until 

 later. 



From a point about 5 mm. in front of the middle of the suprasylvian sulcus a furrow 

 (which may attain a length of 20 mm.) passes obliquely forward and inward to end upon 

 the anterior pole of the hemisphere. For reasons which will be discussed later, I shall 

 distinguish this sulcus by the not-obviously apjiropriate name " coronalis." In almost 

 all cases the posterior part of this furrow is bent backward and inward toward the lateral 

 sulcus (fig. 2). We may distinguish this little fragment from the rest of the sulcus by 

 the letter e. 



Midway between this sulcus and the mesial border there is a very short furrow, the 

 direction of which is by no means constant. In most cases, hoAvever, it is directed 

 laterally and forward. For the present I shall call it the " sulcus y," 



Upon the orbital surface of the hemisphere there is a small sulcus of very variable 

 size, depth, and shape alongside the olfactory bulb. It is the orbital sulcus. In some 

 brains it is either quite absent or represented only by a very shallow dej)ression. 



Immediately in front of the lower extremity of the suprasylvian sulcus (which is 

 generally exposed in the genus Lemur) there is often a small oblique sulcus in the 

 orbital margin. This I shall call " diagonal." 



Near the floccular notch (in the caudal margin of the hemisphere) there is generally a 

 small oblique sulcus, which may or may not extend into the floccular depression and 

 overlap the sulcus c. It may be distinguished for the present by the letter g. 



[In the foregoing enuniciation of theise sulci I have deliberately used term.s which no other writer has employed 

 in reference to the Lemur's brain, not only to avoid the hopeless confusion which the varied nomenclature of 

 Eeddard, Ziehen, Chudzinski, and Flatau and Jacobsohn wouki entail, but also for morphological reasons, which will 

 appear later and, I believe, justify this course of action.] 



In different individuals of the genus Lemur the cerebral hemisphere exhibits slight 

 variations in size, shape, and the arrangement of its sulci. 



The only writer, so far as I can remember *, who has even so much as hinted at the 



* As most of the literature is not at present available, I am unable to consult the memoirs of Gervais in regard 

 to this point ; but, unless my memory belies mc, this statement is correct. 



