BASICRANIAL REGION OF THE LEMUROIDEA 431 



bulla on the lower surface, then passes directly upward (craniad) through 

 the margin of the septum of the cavum bullae, passing into the cranial 

 cavity at the apex of the enlarged cochlea (Van Kampen, 1905, page 

 67G). In the only known skull of " Anaptomorplius" homunculus the 

 whole lower wall of the l)u]la is broken away, so the place of entry of the 

 carotid into the cavum bulliE is not indicated. To the small cochlea is 

 attached a remnant of a long septum, which may have carried the carotid 

 canal. 



The chief conclusions which may provisionally be drawn regarding the 

 course of the main branch of the internal carotid in the Lemuroidea are 

 as follows : 



(1) That most of the Lemurifonnes retain a primitive lemuroid con- 

 dition, in that the arteria promentorii, or main branch of the internal 

 carotid, in passing through the bulla, runs forward in a bony tube along 

 the outer side of the cochlea, or auditory prominence, and pierces the 

 basisphenoid. These forms have no ''foramen lacerum medium," in the 

 ordinary sense of the term, since the point where the carotid pierces the 

 basisphenoid is concealed from below by the bulla. This condition is 

 characteristic of the Kotharctinge, Adapins, Lemurina?, Indrisinse, 

 Archasolemurinse, and Chiromys. 



(2) In the Chirogaleina? the main branch of the internal carotid does 

 not pass through the bulla at all, but enters the brain-case in front of 

 the bulla through the large foramen lacerum medium. This condition 

 appears to be a later specialization. 



(3) Of the Tarsiiformes, the Upper Eocene Necrolemur had no 

 foramen lacerum medium, and the main l^ranch of the internal carotid 

 apparently entered the \>u\\a tiirough a carotid foramen on the inner or 

 medial surface of the bulla. Whether the arteria promentorii ran through 

 a tube over the auditoiw prominence is not known. In Tarsiiis the 

 carotid foramen is enlarged and shifted to the ventral surface of the 

 bulla, and the carotid canal, or tube, only touches the cochlea at its apex. 

 In "Anaptomorplius" the carotid probably pierced the bulla either as in 

 Necrolemur or as in Tarsius, but its course inside the bulla is doubtful. 



(4) In the Lorisifonnes (Ix)risidfe) the main branch of the internal 

 carotid did not pierce tlie bulla at all. hut entered the brain-case through 

 the widely open foramen lacerum uicdiuiu, a condition which is probably 

 secondary, as in Chirogaleina^. 



Thus the true Lemuriformes, with the exception of ihc riiirogaleinae, 

 are distinguinbcd by retaining an apparently primitive arrangement of 

 the carotid foraniiiui and canals; XrcrolniiNr and the Tarsiida, including 

 "Anaptomurpkas' Iioiiiuik iilus. arc cbaractcrizt-d by a more advanced 



