BASICRANIAL REGION OF THE LEMUROIDEA 429 



over the auditory prominence, or cochlea; the canal divides into two 

 branches for the arteria promentorii and the art. stapedia respectively. 

 The arteria stapedia traverses tlie stapes and then runs upward through 

 the periotic, this branch being homologous with the ramus superior of 

 Insectivores. The arteria promentorii runs forward in the outer wall 

 of the anterointernal extension of the bulla, pierces the basisphenoid, 

 and emerges into the cerebral chamber lateral to the sella turcica, as in 

 Insectivores. 



In Notharctus, as shown in an American Museum specimen, and in 

 Aclapis, as shown in Stehlin's material, the foramina and canals for the 

 arteria promentorii and the art. stapedia were identical in position with 

 those in Lemur and Propiikecus and quite different from those of the 

 Tarsiiformes. In modern Lemuriformes, and very likely in Notharctus 

 and Adapis, the arteria promentorii was small and the major part of the 

 blood supply of the cerebral arteries was furnished by the vertebral 

 arteries through the ramus communicans posterior. In the Tarsii- 

 formes, on the other hand, as well as in the whole suborder Anthropoidea, 

 the vessel which is supposed to be homologous with the arteria pro- 

 mentorii is enlarged, forming the typical "internal carotid" and furnish- 

 ing a large part of the l:)lood supply of the cerebral arteries. Tandler's 

 observations and conclusions suggest that the latter condition has been 

 derived from the former. 



Another distinction between the Lemuriformes and the Tarsiiformes 

 is that in the former the stapedial artery and its ramus superior are 

 always well developed, while in the latter they are typically reduced or 

 wanting. 



These facts and considerations afford further evidence for referrincr 

 Notharctus and Adapis to the Lemuriformes rather than to the "ISTeo- 

 pithecini" of Wortman (1903, pages 172-174), which is an unnatural 

 assemblage composed of the Adapida3 and all the families of the Antliro- 

 poidea. 



While the typical Lemuriformes (including the Lemurina', the In- 

 drisidse, and the Chiromyidffi) have the main branch of the internal 

 caiotid passing over tlie cochlea and through the tympanic cavity, a 

 puzzling exception to this rule is furnished by the mouse lemurs and 

 other dwarf lemurs of the subfamily Chirogaleinae. In these genera the 

 observations of Mivart. ^^■illg('. 'l^mdler, and \i\n Kampen have estab- 

 lisbed tlio fact that the main l)ranch of the internal carotid does not 

 l)ass through ihc tympanic cnvitv at ;ill. l)ut enters tlie skull through a 

 pair of large foramina laccra media"' iiii mediately antornintoninl to tlie 



"Foramen lacenim anterius of Ocimau aulliois. 



