BASICRANIAL REGION OF THE LEMUROIDEA 427 



In the members of the family Lorisidie, which includes all the existing 

 non-Malagasy lemnroids except Tarsius, namely, the Galagos and Pottos 

 of Africa and the Lorises of the Far East, the auditory region agrees 

 with that of the Tarsiiformes in that the ectotympanic lies outside the 

 bulla, of which it fornas the outer margin. In the Lorisid^, however, 

 the ectotympanic does not form a protruding tubular auditory meatus, 

 but merely a circular opening into the bulla; in these forms the mastoid 

 is much inflated and its sinus extends widely into the inflated medial 

 wall of the bulla, a character foreshadowed in Necrolemur of the Tarsii- 

 formes. The Lorisidge in many respects mingle the characters of the 

 true Lemuriformes with those of the Tarsiifonnes and are here referred 

 to an intermediate series which may be named Lorisiformes. 



The complex relations of the branches of the internal and external 

 carotid arteries to the auditory region and to other parts of the cranium 

 have been explored in the Primates, especially by Tandler (1899), Winge 

 (1895), and Leche (1896), the work of Tandler being the most compre- 

 hensive. Van Kampen (1905) has partly applied their results in his 

 work on the tympanic region of mammals. Wortman (1903) attempted 

 to apply this line of investigation to the study of fossil Primates, but as 

 he was equipped with the imperfect data furnished by Huxley and 

 Mivart, rather than with the fuller and more correct results of Tandler, 

 Zuckerkandl, and others, his interpretation of the conditions in recent 

 and fossil Primates is partly erroneous. Stehlin (1912) lias made a 

 thorough study of the basicranial region of Lemur and Adapis with 

 special reference to the course of the internal carotid. 



Tandler's researches are especially important as furnishing a rational 

 explanation of the complex and varied arrangements of the carotid 

 arteries and their brandies throughout the mammalia. The internal and 

 external carotid arteries are regarded by embryologists as having been 

 derived phylogeiietically from the afferent vessels of the branchial arches 

 of lower vertebrates. In mammals some of the minor branches belonging 

 to adjacent arclies tend to anastomose with each other, and when this 

 happens, at-cording to Tandler's theory, the terminal branches of the 

 more anterior arches are captured, as it were, by the main trunks of the 

 more posterior arches. In this way some of the minor camtid branches 

 in the orbit, which appear to liave been supplied originally hy tlie hist 

 visceral arch, are found in certain mlult mammals to be supplied by the 

 main vessel of the second viscci'al ai-cli. which is the stapedial artery. 

 Again, the minor branches of the stapcilial artery arc oficn captured by 

 the main li'unk of tlic ihii-d viscci'al arch, which is the external carotid 

 artcr}', aiiil as a I'csnlt of this captiii-c the stapedial arteiT \{<c]\' is often 



