GREGORY: NOTHARCTUS, AN AMERICAN EOCENE PRIMATE 



177 



of the cavity, medial to the Eustachian opening, beneath the bulla. The whole region so closely resembles 

 that of Propithecus that we may safely assume that the course of the entocarotid and its branches was 

 essentially similar. The posterior carotid foramen lies at the posterior end of the bulla and the foramen 

 lacerum medium is roofed over. 



Chiromyid^ 

 Text Fig. 68 



Comparison of the researches of Zuckerkandl (1900, pp. 160-162) and Tandler (1899, p. 762) shows 

 that the whole course of the art. promontorii and art. stapedia in Chiromys is similar to that of Lemur 

 and Propithecus. The posterior carotid foramen hes at the posterior end of the bulla 3 mm. below 

 the stylomastoid foramen (Zuckerkandl). Inside the bulla, van Kampen (1905, p. 664) found the 

 carotid canal in its usual place on the cochlea. The art. promontorii is very small, but as in other Lemurs 



A communicans 

 posterior 



^A. carotis exl, 

 »A thyreoid sup. 



Veriistlung der A. carotis interna unci der A. stapedia. 



Fig. ()8. Eiagrani showing the course of the internal carotid artery and its connections in Chiroiin/.s. After Zucker- 

 kandl. 



the stapedial branch is larger. The foramen lacerum medium is roofed over by the bulla and the art. 

 promontorii enters the brain-cavity through the remnants of this foramen, namely a narrow sUt, lying 

 above the Eustachian foramen and lateral to the septum that divides the cavity of the bulla into medial 

 and lateral moieties. The cerebral arteries draw their chief supply from the vertebral arteries. 



From the foregoing descriptions it will be seen that the course of the two main branches of the carotid 



