194 



GREGORY: NOTHARCTUS, AN AMERICAN EOCENE PRIMATE 



verified by the writer. It is therefore retained, with some modifications, in the present paper, as a con- 

 venient mnemonic device, as a record of conclusions, and as a working hypothesis for further investiga- 

 tion. 



In estimating the degree of homological agreement or affinity between two given forms, it seems 

 important to remember that the "whole is greater than any of its parts" and that, as Linnseus is reported 

 to have said, "the genus makes the character, not the character the genus." To the writer a sufficient 

 reason for regarding two animals as divergent representatives of a single family is not that they resemble 

 each other in any one character or in several characters taken independently, but that in all views of the 

 skull and skeleton a common general stamp or underlying "family resemblance" is revealed, beneath 

 many conspicuous differences in detail. 



In any such case, the "underlying family resemblance," the effect of the whole, is apt to be lost as 

 soon as we begin to record at great length the details that differentiate the skulls from each other. But 

 each of these important details should be viewed in its correct and due relation to the organism as a 

 whole and especially should such differences be considered as an expression of specific functions and habits, 

 which differentiate the genera in question both from each other and from their common ancestor. In 

 the case of Adapts and Nothardus the "family resemblance" is indicated in the accompanying illustra- 

 tions of three aspects of the skull. The skull of Nothardus, as a whole, in general appearance and in 

 fundamental construction, is closer to that of Adapis {Leptadapis) magnus var. leenhardti (Stehlin, 

 1912, pp. 1278, 1279, figs.) than to that of any other known primate outside of its own subfamily. There 

 is, in fact, a striking agreement in general proportions of the face and brain-case, in the gentle inclination 

 of the face to the basicranial axis, in the relatively slight expansion of the brain-case, in the sharp con- 

 striction of the skull behind the orbits, in the powerful build of the zygomata, and in the prominence of 

 the sagittal and lambdoidal crests. 



When the "underlying family resemblance" mentioned above is analyzed into its component parts, 

 it yields a considerable list, comprising some thirty-odd characters of the skull and dentition (see page 

 184 above). Of these, eight of the more fundamental ones are preserved in several other families (Lemu- 

 ridse, Indrisidse, etc.) which the writer believes to be derived from the ancestral Adapine-Notharctine 

 stock, and which may therefore be considered as superfamily characters (listed under Lemurif ormes) ; 

 the remainder, comprising about twenty-five characters exclusive of those of the limbs, are diagnostic for 

 the Adapidse as here defined. 



Important evidence for the relatively close relationship of Adapis and Nothardus to each other and 

 to the modern Lemuridse and Indrisidse rather than to the Tarsiidse and the higher primates is afforded by 

 the construction (see pages 161-178 above) of the whole basis cranii, and especially of the auditory region, 

 ior Adapis and Nothardus preserve with slight modifications what is regarded by the writer as the primi- 

 tive condition of the auditory region for the whole lemuriform series. The enclosure of the tympanic 

 annulus by the expanded periotic bulla, the topographic relations of the osseous carotid canal and its 

 stapedial branch to the cochlea, the contact between the bulla, the pterygoid plate of the alisphenoid 

 and the entoglenoid region of the squamosal, the substantial identity in the positions and relations of 

 nearly all the foramina of that region are all judged by the writer to outweigh in phylogenetic and syste- 

 matic significance the moderate divergence in the dentition in the two subfamilies. 



The assignment of a high systematic value to the characters of the auditory region is a natural result 

 of the fruitful investigations of Winge, Forsyth Major, van Kampen, Stehlin, and others upon the 

 morphology of this region in primates and in many other orders of mammals. For some years past the 

 writer has applied and verified their results especially in the study of the marsupials, creodonts, Fissipedia, 



