174 



GREGORY: NOTHARCTUS, AN AMERICAN EOCENE PRIMATE 



In Talpa, which also represents the lipotyphlous insectivores, the course and distribution of the main 

 branches of the entocarotid in general conform to the plan described above for Erinaceus. In Tupaia, 

 representing the Menotyphla, which may well be allied to the Lemuroidea, the entocarotid likewise divides 

 into two main branches — the art. promontorii and art. stapedia, which run in bony canals in the tym- 

 panic fossa (Hyrtl) ; according to Hyrtl's figure {op. cit., Taf. ii, fig. 15) the ramus inferior of the stapedial 

 artery is large and issues from the tympanic cavity anteriorly as in Erinaceus. 



Lemurin^ 



Lemur. — According to the collective results of Winge, Tandler, van Kampen (pp. GfiO, (JGl), and 

 Stehlin (pp. 1207, 1202), here verified as far as possible in the dried skulls (Plates XLIII, XLIV, XLV), 

 the entocarotid in Lemur, enters the bulla at its posteroexternal border medial to and below the stylomas- 

 toid foramen (/. c. p.). 



Wortman (1903, p. 166) locates the carotid foramen in Lemur catta at the posterointernal angle 

 of the bulla, between the bulla and the basioccipital in the region where it enters in many modern 

 carnivores. But this interpretation is contrary to the statement of Tandler (1899, p. 761): "Dieses 

 Gefass, [arteria carotis interna], dessen Abgangsweise von der Carotis communis schon beschrieben wurde, 

 zieht gerade cranialwarts und gelangt an die hintere Wand der machtigen Bulla, zieht an dieser entlang 

 und tritt in die Bulla selbst erst hoch ober, knapp unterhalb des Austrittes des Facialis ein." That is, 

 it enters immediately below the stylomastoid foramen, as held also by Winge, van Kampen (p. 660) 

 and Stehlin (1912, p. 1207). As may be seen in the dried skull, the opening which Dr. Wortman identifies 

 as the carotid canal leads directly into the cranial cavity in the region of the posterior cranial nerves, 

 and it is rightly regarded as a part of the foramen lacerum posterius by van Kampen (p. 658) and by 

 Stehlin (1912, p. 1207). 



The above described posterior carotid foramen (/. c. p.) on the posteroexternal wall of the bulla leads 

 into a short carotid canal that runs forward, inward and upward to the external face of the auditory promi- 

 nence or cochlea; the canal and its vessel then immediately divides into two branches named respectively 

 (a) arteria stapedia and (b) arteria promontorii. 



(a) The arteria stapedia, which is much the larger of the two branches, at first enclosed in a canal, 

 turns sharply upward, bends outward and pierces the stapes; thence it enters the Fallopian aqueduct 

 for the facial nerve (Winge) and following this canal part way through the petrosal it leaves it and emerges 

 into the brain-cavity on the outer upper slope of the petrosal through a small foramen immediately postero- 

 internal to the postglenoid foramen (Stehlin). It at once gives off the arteria meningea media, after 

 which it turns forward, and running along a deep venous groove in the squamosal on the external basal 

 corner of the brain-cavity, it emerges from the brain-case into the orbit, through the " cranio-orbital 

 foramen" (Stehlin). This foramen is dorsolateral to the optic-sphenorbital-rotundum group and is 

 near the dorsal border of the alisphenoid. After leaving the cranio -orbital foramen the stapedial artery 

 crosses the orbit and joins the ophthalmic artery. 



(b) The arteria promontorii (which is probably homologous with the main internal carotid of man) 

 I'uns in a canal along the outer face of the cochlea (Plate XLV) ; it lies in front of the fenestra cochleae (seu- 

 rotunda) (contrast the Nycticebidae, p. 180) and is parallel to the oblique septum that incompletely 

 separates the hypotympanic from the true tympanic cavity. Continuing forward along the outer surface 

 of this septum and immediately internal to the Eustachian foramen (ostium tubir) the canal runs in the 

 outer wall of the anterointernal extension of the bulla, gradually passing upward through the petrosal. 



