492 ox THE ZOOLOGICAL POSITIOX 



It cannot be doubted, from an examination of its entire anatomy, 

 that Tarsias is a i-euiarkably primitive mammal which has early 

 acquired an over-specialisation in vision and in poweis of frog- 

 like arboreal leaping. In these two features it roughly resembles 

 Galago, a,nd it may be doubted if, ha<l this likeness not been so 

 apparently exact, zoologists would have classed Tarsius in the 

 Lemuroidea with so much coufideuce. One primitive feature 

 retained by the specimen dissected is the presence in the carpus 

 of an element which I can only homologise as a second os centrale. 

 This small bone has not previously beeir described, and its de- 

 tection v/ithout the use of X-rays would be rather a matter 

 of chance. The true os centrale (os accessorium, Burmeister) 

 articulates with carpale I., II., and III., as well as with the 

 scaphoid and semilunar (thus dift'ei'ing from the condition as 

 described and figured by Burmeister). 



The second os centrale exists on the radial side of the carpus 

 in the gap between carpale I. and tlie scaphoid ; it does not 

 actually articulate with aiiy bone, being held in place by fibrous 

 tissue. It is not situated in tendon, but is enveloped in the 

 capsule of the carpal articulation. Should this small bone prove 

 to be a constant element in the carpus of Tarsius, it would furnish 

 very interesting evidence to which it is hoped attention will be 

 given by other observers having command of material. Tarsms 

 differs from all members of the Lemuroidea in certain of its 

 external characters : — (i.) In having the nostril completely 

 ringed by the meetiiVg of the lateral and medial nasal processes. 

 In this encircling of the nares it resembles all members, and 

 surpasses some, of the Anthropoidea. (li.) In having the upper 

 lip simple in the mid-line. There is no lemurine incisura 

 between maxillary processes, but a truly Simian philtrum com- 

 posed of medial nasal processes, (iii.) The hair-tracts resemble 

 those of the highest of the Anthropoidea, far more nearly than 

 they do those of the Lemuroidea,, or even the lower Anthro- 

 poidea. (iv.) The digital formula differs fi'om that typical of the 

 Lemurs, the middle line digit being the longest, (v.) The meta- 

 carpal formida shows the same primitive and non-lemurine 

 features, (vt.) The external genitalia, especially those of the 

 female, are formed upon a plan altogethei- unlike that seen in 

 the Lemui'S and resembling that typical of the highest 

 Anthropoidea. 



In its internal anatomy Tarsius differs from all members of the 

 Lemuroidea in (vii.) its dental characters ; (viii.) in the forma,- 

 tion of the auditory bulla ; (ix.) in the form and fate of the 

 tympanic bone, and in the inception of an external auditory 

 meatus. Combined with these last two charactei-s is (x.) the 

 non-lemurine cranial course of the internal cai'otid artery. In 

 the formation of the orbit two characters, typical of the Anthro- 

 poidea and differing widely from anything seen in the Lemurs, 

 are conspicuous : (xi.) with the inner wall of the orbit the 

 OS planum of the ethmoid enters, and (xii.) the orbit is furnished 



