372 MR. R. OWEN ON THE OSTEOLOGY OF 
sition and proportions of the teeth, which afford unfailing and impassable generic 
distinctions between Man and the Ape!. 
To place this proposition in the most unexceptionable light, I have selected the cra- 
nium of a human idiot, in whom nature may be said to have performed for us the ex- 
periment of arresting the development of the brain almost exactly at the size which it 
attains in the Chimpanzee, and where the intellectual faculties were scarcely more deve- 
loped. Yet no anatomist would hesitate in at once referring this cranium to the human 
species. 
A detailed comparison with the cranium of the Chimpanzee or Orang shows that all 
those characters are retained in the idiot’s skull which constitute the differential features 
of the human structure. 
The cranial cavity extends downwards below the level of the glenoid articulatory 
surfaces. 
The nasal bones are two in number, and prominent. 
The jaws and teeth exhibit the Bimanous characters as strongly as in the most elevated 
of the human race. The cuspidati do not project beyond the contiguous teeth, and con- 
sequently there are no interruptions in the dental series, as in the Orangs, where they 
are required to lodge the disproportionate crowns of the canine teeth. 
With respect to the zoological relations subsisting between the Chimpanzee and Orang, 
the differences above mentioned warrant their being regarded as types of two distinct 
subgenera. The characters, however, proposed by M. Geoffroy St. Hilaire®, being de- 
rived from immature specimens, require to be altered. 
Subgenus Trogiopytss. 
Muzzle long, truncated anteriorly ; strong supraciliary ridges, behind which the fore- 
head recedes directly backwards ; no cranial ridges. 
Facial angle 35°, excluding the supraciliary ridges. 
Auricles large. 
Thirteen pairs of ribs ; bones of the sternum in a single row. 
Arms reaching below the knee-joint. 
Feet wide ; hallux extending to the second joint of the adjoining fae. 
Canines large, overpassing each other, the apices lodged in intervals of the opposite 
teeth. 
' Perhaps one of the best exemplifications of the degree of approximation which the Quadrumana make 
towards the human species, is the position assigned by naturalists to the adult Orang before its identity with 
the immature Satyrus was established. See ‘ Annales du Muséum,’ tom. xix. p. 89; Latreille, ‘Fam. Nat. du 
Régne Animal,’ p. 44; and Fischer, ‘ Synopsis Mammalium,’ p. 32, who, without entering into the particular 
differences, observes, ‘‘Sunt qui hanc speciem (Simia Wurmbii) pro Sim, Satyro adultaducant. Permulte tamen 
sententiz isti repugnare videntur.” 
* Annales du Muséum, tom. xix. p. 87, 

