On the Brains of two Sub-Fossil Malagasy Lemuroids. 47 



in their posterior moiety and suddenly attenuated anteriorly. Apart 

 from the Sylvian fissure, the brain surface of Microcebus is perfectly 

 smooth, whilst the cast of the fossil shows a greater complication than 

 in any other known Lemur id. This is in accordance with what might 

 have been anticipated, Globilemur being larger than any living 

 Lemurid, and, as Broca states : " Un cerveau qui grandit doit seplisser 

 sous peine de dechoir* " ; this, in my opinion in fact, means that for 

 economy of space plication is resorted to as a means of increasing 

 the surface. 



In the arrangement of its convolutions (fig. 2), the fossil departs 

 likewise from what is known of Lemurid brains, and approaches 

 rather more to what is presented by some of the larger Cebidce and 

 Cercopithecidce. In Lemurids the fissures and the corresponding con- 

 volutions show a tendency towards a longitudinal arrangement, quite 

 different from the more radiating direction exhibited by the fossil. Its 

 Sylvian fissure (s.f.), on the other hand, corresponds in its more vertical 

 direction to what we find in Lemurids, and in this respect departs 

 more from the Old and New World monkeys, though less from the 

 former than from the latter. The character mentioned is in relation 

 with the development of the occipital lobe, the Sylvian fissure being 

 always more horizontally directed in those brains in which the 

 occipital lobe is well developed and in which, as a consequence, the 

 cerebellum is covered. In fact, in Globilemur, the cerebellum is much 

 less overlapped than in the monkeys. 



In the lesser development of the frontal lobes we find a further 

 agreement with Lemurids as compared with monkeys, and equally 

 so in the more macrosmatic character of the brain of Globilemur, as 

 revealed by its voluminous olfactory lobes. 



I shall not enter into farther particulars as it is never safe to 

 attempt to make out the exact homologies of the fissures in a cast of 

 the brain cavity. Moreover, in this case, I find that the two sides of 

 the hemispheres do not agree in every respect, owing partly to the 

 incomplete condition of the skull and partly to the difficulties encoun- 

 tered by the artist in the moulding. 



II. Megaladapis madagascariensis, Maj. 



The second cast, from the brain-cavity of Megaladapis madagas- 

 cariensis, is in many respects the very opposite of Globilemur. First, 

 as to size,— from the dimensions of the respective skulls, the size of 

 the first named animal (Megaladapis) may be approximately calcu- 

 lated as double that of the last (Globilemur), whilst in bulk the brain 



* Paul Broca, " Anatomie comparee des Circonvolutions Cerebrales. Le grand 

 lobe limbique et la scissure lhnbique dans la serie des Mammiferes," ' Kevue 

 d : Anthropologic,' II, vol. 1, 1878, p. 413. 



