CiRE(;OKY: NOTIIARCTVS, AN AMERICAN EOCENE PRIMATE 



179 



Lemur, Propiihecus, and all other true lemurs except the Chirogaleinffi, the main internal carotid (art. 

 promontorii) was small and the cerebra received their supply chiefly from the vertebral arteries; whereas, 

 as noted by Tandler and by Wortman (1903, p. 175), in Tarsius and all the Anthropoidea (including New 

 and Old World monkeys) the arteria promontorii or true entocarotid is greatly enlarged and supplies the 

 chief arterial supply for the cerebra. 



Chirogalein^ 

 Plate LIV 



In Microcebus furcifer of the Chirogaleina^ the observations of Mivart, Winge, Tandler and \'an 

 Kampen (pp. 661, 662) collectively show that the main entocarotid branch runs through the widely open 

 foramen lacerum medium and also pierces the basisphenoid (as in Marsupials) ; that the posterior carotid 

 foramen (/. c. e.) is also present but small; as in Chiromys it lies near the foramen lacerum posterius, 

 near the supposed junction of the bulla and the mastoid. Thus Microcebus furcifer agrees with the 

 Nycticebidse in that the main entocarotid branch enters through the foramen lacerum medium, while 

 the posterior branch is small. In the other species of Microcebus, however, the foramen lacerum medium 

 is said to be more or less roofed over by the anterointernal extension of the bulla (van Kampen). In 

 Chirogale (Plate LIV) and Atililemur there are large carotid canals (/. /. 7n.) piercing the basisphenoid, but in 

 Myoxicehus (Plate LIV), the skull of which appears to me to be related in structure to that of Atililemur, 

 these openings are much reduced. According to the view here adopted provisionally, the branch which 

 enters through the foramen lacerum medium and the basisphenoid in Microcebus furcifer is homologous with 

 the arteria promontorii of Lemur, with the anterior branch in the Nycticebidse and with the main internal 

 carotid in man. The small posterior branch may be the art. stapedia. 



In the cases where the foramen lacerum medium is partly roofed over by the bulla the art. promontorii 

 may have passed through the bulla, entering the bulla by the posterior carotid foramen and entering the 

 brain-cavity through the anterior part of the roof of the external chamber of the bulla. 



The apparent shifting of the main carotid artery, which in most lemurs pierces the anterior wall of 

 the tympanic cavity, but in Nycticebidse and Chirogaleinse enters through an anterior carotid foramen 

 (/. /. m.) in front of the bulla, is explained by van Kampen (1905, p. 383) as follows: 



\\'inc'za found in .st'\'eral placental inaninials that ontogenetically the carotid, before it reaches tlie carotid foramen 

 I f.r. \ runs along tlie ventral side of the cochlear portion of the otic capsule. This fact explains the difference hetween 

 adult phicentals [of different groups], in which the artery either tra\'erses the tympanic cavity, or i-emaiiis medial to it, as 

 in all monotremes and marsupials. This is connected especially with the origin of the ventral wall of the tymi)anic cmx ity. 

 When it is formed from the bones of the basis cranii that are medial to the petrosal (namely, l)asioccipital, l)asisphenoid) 

 then the carotid comes to lie inside the tympanic cavity {Myrmccophaga, most insectivores) ; in other cases it depends 

 upon where the ventral wall of the tympanic cavity rises from the petrosal, whether the carotid sliall run lateral to it and 

 thus inside the ca\ ity ( 'iiipitia, most Prosimife and Simife), or medial to it (most XriKirtlirn, ( 'arnixora, Fngulata, Lorisidte, 

 etc.). The course of the carotid may in this respect be different in nearly related animals (cf. among X( narthra, Prosimise, 

 Rodent ia). [Translation.] 



LOKISID.E 

 Plate XLIX (Fvrodldlnis) 



In this family the divided "entocarotid" enters the brain-case by two widely separated routes. 

 (1) The largest branch enters in front of the bulla through the widely open foramen lacerum medium. 

 Tandler regards this branch as homologous with the main internal carotid of man and with the "arteria 



