428 AV. K. GREGORY- — NOTHARCTUS AND LEMUROIDEA 



al)seiit in the adult, although present in the embryo (as in man). Ac- 

 cording to this theory, the recent Insectivores retain an arrangement of 

 the carotid branches which is more primitive than that which is char- 

 acteristic of the Lemuriformes, as described below, while these in tarn 

 are more primitive than the Tarsiiformes and the higher Primates. 



In Erinaceus, according to the researches of Hyrtl, Tandler, and 

 others, the internal carotid enters the bulla from the rear, through a 

 foramen that is incompletely separated from the stylomastoid foramen. 

 Inside the bulla the arter}^ divides into two main branches, named the 

 arteria pi'omentorii and the art. stapedia. The art. promentorii, which 

 is homologous with the internal carotid of man, bends around over the 

 cochlea, or auditory prominence, and, passing forward and inward, pierces 

 the side of the basisphenoid, as in Marsupials, Centetes and Lemur; 

 entering the cerebral chamber lateral to the sella turcica, it joins the 

 main cerebral artery. The stapedial branch is of large size, and after 

 piercing the stapes runs forward in a groove in the roof of the t3Tnpanic 

 cavity, issuing into the temporal fossa through a notch, or foramen, in 

 the tympanic process of the alisphenoid, posteroexternal to the foramen 

 ovale ; the carotid notch or foramen transmits an important branch named 

 the "ramus inferior," which runs forward to the orbit and gives rise to 

 several minor l^ranches. The other branch of the stapedial artery 

 ("ramus superioi^') comes off from the ramus inferior in the anterior 

 part of the tympanic fossa ; it passes backward and upward through the 

 petrosal. In Tupaia, representing the suborder Menotyphla of the order 

 Insectivora, Hyrtl's figures show that the internal carotid likewise divides 

 into two main branches — the art. promentorii and art. stapedia — which 

 run in bony canals in the tympanic cavity; the ramus inferior is large 

 and issues from the tympanic cavity anteriorly, as in Erinaceus. 



In all the recent Lemuriformes the internal carotid differs from that 

 of the insectivores chiefly in that the ramus inferior of the stapedial 

 artery is always wanting, and consequently there is no carotid foramen 

 in the tympanic region of the alisphenoid — apparently, according to 

 'J'andler's view, because its terminal branches have been captured bv the 

 external carotid. 



The internal carotid in typical lemurs enters the bulla on its postero- 

 external border medial to and below the stylomastoid foramen.* This 

 posterior carotid foramen leads into a short carotid canal, which runs 



* Doctor Wortman (1903, page 167) errs in locating the carotid foramen of Lemur on 

 tlie posterointernal border of the bulla. The foramen at that point (marked cc in his 

 figure 101, page 166), according to Van Kampen (1905, page 658) and other authorities, 

 is a part of the foramen laoerum posterius ; it leads directly into the cranial chamber 

 and plainly gives exit to a cranial nerve, probably the eleventh. 



