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GREGORY: NOTHARCTUS, AN AMERICAN EOCENE PRIMATE 



promontorii " of Lemur, a view which is adopted by StehUn (1912, p. 1212). Winge's opposing view 

 (cf. van Kampen, p. 672) that the main internal carotid in the Nycticebidse is not homologous with the 

 arteria promontorii of Lemur, appears to the present writer improbable, on account of the structurally 

 transitional stages offered by the Chirogaleinee (vide supra). 



(2) The posterior branch (Plate XLIX), which is extremely small, enters the posterointernal region 

 of the bulla immediately in front of the foramen lacerum posterius and passes over the cochlea, behind 

 the fenestra cochleae (rotunda). It is probably the "art. stapedia," but this identification lacks verifica- 

 tion and is opposed by Winge, who held that it represented both the art. promontorii and the art. stapedia 

 of Lemur (van Kampen, p. 672). At any rate, the Lorisidse are characterized by the widely open foramen 

 lacerum medium and by the reduced posterior carotid foramen if.cp.) 



In Necrolemur, which in many respects combines characters of the Lorisidse with others of the Tar- 

 siidge, there is a prominent foramen which is probably the internal carotid foramen located on the inner 

 wall of the bulla immediately in front of the foramen lacerum posterius. In front of the bulla and lateral 

 to the anteromedial protuberance there is a foramen which may be the opening of the eustachian tube 

 since it strongly resembles that opening in the Nycticebidte. This interpretation is based upon a skull 

 of Necrolemur antiquus in the British Museum and upon another skull in the Peabody Museum at Yale 

 University (Plate LI). It also accords with Dr. Stehlin's identification of the carotid foramen (1916, 

 p. 1349). Thus, there was no foramen lacerum medium in Necrolemur and the carotid passed through 

 the bulla, although its precise course is not known. 



TARSIIDiE 



Plate LI 



In Tarsius the internal carotid pierces the bulla, passing through an osseous canal located in the middle 

 of the bulla and a little in front of the external auditory meatus. There is no foramen lacerum medium, 

 this region being completely closed by the greatly inflated bulla, as it is in Necrolemur. Winge thought that 

 there was a small opening for the stapedial artery in the posterior part of the bulla, but this was not con- 

 firmed by van Kampen (p. 676), who found a canal for the stapedial artery piercing the stapes, inside 

 the bulla where it is given off from the canal for the main entocarotid artery or arteria promontorii; thus, 

 according to van Kampen, the arrangement of the stapedial artery is fundamentally as it is in the Lemuridse 

 (see below). The stapechal canal is preserved in the specimen of Tarsius shown in Plate LI, but I was 

 unable to observe its junction with the main canal. The vessel which traverses the main canal and gives 

 off the stapedial artery is undoubtedly the homologue of the "internal carotid" of man; it is probably 

 also homologous with the entocarotid of Lemur (which likewise divides into two branches inside the bulla) . 



In Tetonius {" Anaptomorphus'' ) which is provisionally referred to the Tarsiidse, the strong similarity 

 of the parts of the bulla preserved to that of Tarsius suggests that the carotid likewise ran through a 

 large bony canal, but no remains of this canal were recognized; very possibly it ran along the lateral 

 face of the cochlea in the septum between the true tympanic and the hypotympanic cavity. (Plate LI.) 



Platyrrhini 

 Plate XLIX (Alouaiia) 



In the New World monkeys the opening of the carotid canal faces posterointernally and it is generally 

 near the posterior border of the bulla. The canal is much larger than in any of the Lemuriformes and 



