426 AV. K. GREGORY NOTHARCTUS AND LEMUROIDEA 



II. On the Classification and Phylogeny of the Lemuroidea 



ON THE BASICRANIAL REGION OF THE LEMUROIDEA 



As the characters of the base of the cranium are of great systematic 

 and phylogenetic importance in the Primates, as well as in all other 

 mammals, I may begin by describing in a general way the principal 

 types of auditory bull^ in the Lemuroidea and the principal relations 

 of the internal carotid artery and its branches to the osseous parts of the 

 cranium in that group. 



The structure of the auditory bullae and surrounding parts has been 

 very carefully studied in the recent Primates by Winge, Leche, Forsytb 

 Major, Van Kampen, and others, whose researches afford adequate data 

 for the interpretation of this region in such extinct Primates as Noth- 

 arctus, N ecrolemur . and Anaptomorphus. In the more primitive form 

 of the auditory region the tympanic membrane is stretched on a ringlike 

 tympanic bone or ectotympanic, and this lies well within the bulla, or 

 tympanic chamber, so as to be completely concealed by the ventral wall 

 of the bulla, as seen from below ; the bulla itself in all Primates appears 

 to be formed as an expanded shell of the periotic. The mastoid region 

 is sometimes inflated. AVith minor variations, this relation of the ring- 

 like tympanic to the inclosing bulla is found in all known members of 

 the Lemurina?, Megaladapinge, Chirogaleinaj, Indrisin^, Archaeolemurinse, 

 and Chiromyidffi, all of which are found in Madagascar. This series of 

 lemuroid families and subfamilies will be referred to below as the 

 Lemuriformes. The material of Adapis, figured by Stehlin (1912), and 

 the American ]\Iuseum material of Notharctus afford proof that in these 

 genera the structure and relations of the auditory bulla and of the ecto-- 

 tympanic conformed to the plan seen in Lemur and Propifhecus, and 

 this fact, in conjunction with other evidence, shows that the Notharctinse 

 and the Adapin», together constituting the family AdapidfE, should be 

 referred to the series Lemurifonnes. 



In the more specialized form of auditory region the ectotympanic bone 

 is not hidden l:)eneath the bulla, but forms its external portion and projects 

 externally in a tubular osseous auricular meatus. The bullae in these 

 forms are much inflated and extended anterointernally toward the mid- 

 line. This series includes, first, the Oriental Tarsius and its extinct 

 Lower Eocene American relatives, Anaptomorphus, Hemiacodon, and 

 their allies, all referred here to the Tarsiidae; and, secondly, the Upper 

 European Eocene genera Necrolemur and Microclicerus, forming the 

 family Microchcerids. This series will be referred to below as the 

 Tarsiiformes. 



