GREGORY: NOTUARCTVS, AN AMERICAN EOCENE PRIMATE 



181 



lies deep in the petrosal; it thus avoids the tympanic cavity and does not pierce the basisphenoid; it 

 emerges into the brain-cavity posteroexternal to the sella turcica (Plate L). 



In Nyctipithecus (Aotus) and Hapale, as observed by Wortman (p. 168), there is a small canal, in 

 front of the foramen lacerum posterius, lying partly between the bulla and the basioccipital and running 

 through the latter into the cranial cavity. I have also observed the same arrangement in Pithccia. Dr. 

 Wortman thinks that this small canal transmits an internal branch of the entocarotid and that it is homo- 

 logous with a certain canal in Lemur, lettered cc. in his Fig. 101, p. 150; it probably is homologous with 

 that canal in Lemur, but that it transmits a branch of the entocarotid is more than doubtful, as indicated 

 above (p. 174); it more probably has nothing to do with the entocarotid but serves for the exit of one 

 of the posterior cranial nerves. 



The stapedial branch of the entocarotid is said to be wanting, at least in Hapale peniciUala and Ateles 

 paniscus, the forms examined by Tandler (van Kampen, pp. 684-688). 



Catarrhini 



The foramen lacerum mcdiiun (foramen lacerum anterius of (lerman writers) has not been developed 

 either in the Old World or in the New World monkeys, since the bulla joins the alisphenoid and basi- 

 sphenoid anteriorly; in the great apes this fissure between the tegmen tympani and the bones in front 

 of it begins to develop but is more or less restricted; in man it is widely open, no doubt secondarily, and 

 through it may be seen the entocarotid which passes across the upper part of the foramen on its way from 

 the carotid canal into the cranial chamber ; but it would be quite misleading to say that in man the inter- 

 nal carotid enters through the foramen lacerum medium; it enters through the carotid canal of the petrosal. 



In the Hylobatidff and the Simiida? the course of the internal carotid is identical with that in man 

 (van Kampen, p. 695) ; in the Cercopithecida; it pierces the bulla more posteriorly, but its course is prac- 

 tically the same (van Kampen, p. 691). 



In man the internal carotid artery ("entocarotid") broadly pierces the petrotympanic (or fused 

 petrosal and tympanic) and, running through the carotid canal into the cranial chamber, gives rise to 

 nine branches and numerous subtli\'isions (Cunningham, 1902, pp. 768-770). The three main branches 

 are the ophthalmic artery and the anterior and middle cerebral arteries. One small branch, given off 

 in the tympanic chamber, the stapedial artery,^ in the embryo pierces the stapes, but later atrophies as 

 it does also in the great apes and Old World monkeys (van Kampen, p. 691 ; Keibel and Mall, II, p. 628). 



Conclusion 



This review may be concluded l)y a summary of Tandler's general hypothesis as to the dei'i\'ation 

 of the various types of entocarotid distribution found in adult mammals. The internal and external 

 carotid arteries are regarded by morphologists as having been derived phylogenetically from the afferent 

 vessels of the branchial arches of the lower vertebrates (Keibel and Mall, II, p. 62S). In mannnals 

 some of the minor branches belonging to adjacent arches tend to anastomose with each other, and when 

 this happens, accortling to Tandler's theory, the terminal branches of the more anterior arches are cap- 

 tured, as it were, by the main trunks of the more posterior arches. In this way some of the minor branches 



' The stapedial artery in many niaininals is coiiiicctKl with the internal maxillary and middle meningeal arteries. Although these 

 two arteries appear to spring from it, their connection with it is nevertheless a secondary one; ontogenetically they are derivatives 

 of the external carotid. The middle meningeal arti-ry runs through the foramen spinosum, which is posteroexternal to the foramen 

 ovale, and enters the cranial cavity. 



