358 PEOF. G. Er,LIOT SMITH OX THE 



Oudemans explains this exceedingly puzzling condition in these words :— " Die Fissura 

 Sylvii zeig-te sich an der rechten Hemisphiire viel mehr ausgeprJigt als an der linken. 

 Nnr der obere Theil derselben war tief einschneidend, der nntere mehr superficiell, 

 besonders an der linken Ilemispliare, wo beide Tlieile selljst getrennt waren. Das wir 

 es hier jedocli gewiss mit der Fissura Sylvii zn tlinn haben, ergab sich durch Ver- 

 gleichung mit den Gehirnen einiger anderen Lemuriden." (Naturh. Yerh. Akad. Amst. 

 xxviii. p. 28.) 



The closing phrase is true, but the writer misses the obvious inference, which must 

 follow from this important fact, viz. — that the Sylvian fissure of the Lemurs is 

 partly represented by the suprasylrian sulcus. In order to evade this conclusion, in 

 deference to the popular belief in the identity of the so-called " Sylvian fissure " 

 of Carnivora and the Prosimian Sylvian fissure, Oudemans is forced to call the lateral 

 sulcvis " suprasylvian." [For if the real suprasylvian is considered as representing 

 the "feline Sylvian," it is not illogical to call the lateral sulcus by the name 

 "suprasylvian," even if such an hypothesis makes it necessary to suppose that the 

 lateral sulcus has disappeared.] It was unfortunate for Oudemans that he did not 

 chance to see such a specimen as my example a ; for then there could have been 

 no doubt that the Lcmuroid Sylvian fissure is also in great part identical with tlie 

 suprasylvian sulcus. 



Chudzinski, who happened to have a specimen Avhich (so far as I a)n able to judge 

 from his unsatisfactory account) resembled my specimen a, failed to recognize the 

 suprasylvian sulcus as the Lemuroid " Sylvian." 



He regards the pseudosylviau sulcus as the Sylvian fissure, and says that it is joined 

 to the rhinal fissure (which he calls the fissure of the olfactory lobes) on the right side 

 but not on the left (Bull. Soc. Anthrop. ser. 4, vii. pp. 13 & 11). [This diff'ereuce between 

 the two hemispheres also seems to occur in my specimen «, but the condition of the brain 

 prevents me from speaking more decisively.] He is then so puzzled by the suprasylvian 

 and postsylvian sulci, that he does not attempt to compare them with the sulci of the 

 Primates, but, like all previous writers, seeks an analogy to the condition found in the 

 Carnivores {op. cil . p. 1()). His specimen seems to have been exceptionally interesting, 

 and it is therefore very disajipointing to find such imperfect drawings and such vague 

 descriptions, from which it is impossible to form a clear conception of the condition. 

 The postsylvian sulcus seems, if I read the account correctly, to be independent of the 

 suprasylvian on the right side ; and the latter appears to l)e so related to the pseudo.sylvian 

 as to be very slightly if at all difteient irom the normal Prosimian Sylvian fissure [but 

 this is by no means clear]. 



One cannot fail to be amazed that Chudzinski, who during the previous year had been 

 studying the brain in Lemur, Kycticcbns, and Indris, should have failed to recognize in 

 the suprasylvian sulcus of Chii'omys the homologue of the upper part of the Sylvian 

 fissure of these Lemurs. 



It is difiicult to i'orm a clear conception of the condition of Owen's specimen from his 

 imperfect lilhographs and vague description ; and the interpretations of it by succeeding 

 writers (such as Pansch, Beddard, and Parker) only tend to still further confuse the issues. 



