THE CHIMPANZEES AND ORANGS. 103 
trum is greater, and the upper and lower costal surfaces are less equal and less approxi- 
mated than in the Chimpanzee. 
The neural spines of the eighth and the preceding dorsal vertebre are shorter than in 
the Gorilla and also than in the Chimpanzee; they are thicker transversely and less 
extended in the axis of the spine, especially at their extremities, which are tuberous, 
not truncate as in the Chimpanzee. 
In the ninth dorsal vertebra (ib. 9) the centrum is relatively larger, and the accessory 
tubercle above the diapophysis is more produced. 
The tenth dorsal vertebra (ib. 10, & figs. 4, 6 & 8) chiefly differs from the preceding 
in the absence of the lower costal surface on each side, as at pl, fig. 4, in which it agrees 
with the tenth dorsal of the Chimpanzee and differs from that in the Gorilla. 
In the eleventh dorsal vertebra the metapophysial tubercle (m) which was slightly 
indicated in the preceding vertebra becomes more distinct. The centrum continues 
to increase in size. 
In the twelfth dorsal vertebra (fig. 2, 12) the centrum continues to enlarge, and the 
neural spine to gain in vertical extent. The metapophyses are well developed: the 
anapophyses (a) may be recognized distinctly : the diapophyses are reduced to smooth 
tubercles without an articular facet. The neural arch of this vertebra contracts in 
breadth below, concomitantly with the modified shape and direction of the lower zyg- 
apophyses (2), which are elongated and incline more obliquely outward than in the pre- 
ceding vertebra. This modification does not characterize the corresponding vertebra 
in the Gorilla or Chimpanzee. The upper emargination of the neural arch is wider in 
the twelfth dorsal, which is distinguishable from the eleventh not only by this character, 
but by the distinctness and greater length of the metapophyses, and by the greater length 
and minor breadth of the part of the neural arch supporting the lower zygapophyses. 
Lumbar Vertebre (P|. XXXV.).—These in the Gorilla and Chimpanzee are four in 
number, by reason of the retention of distinct or free pleurapophyses in the vertebra 
answering to the first lumbar in Man: they are, also, in some adults of both Gorilla 
and Chimpanzee, further reduced by the modification of the vertebra answering to the 
last lumbar in Man, by which it assumes the characters of a sacral vertebra. 
In the full-grown but not old male Gorilla in the Museum of the Royal College of 
Surgeons, the four lumbar vertebre are distinct. ‘I'hey are figured in Pl. XXXV. fig. 1, 
and have longer bodies in proportion to their breadth than in Man; their spines slope 
more downwards, are more expanded at their extremities, and in all but the last are sub- 
bifid, in the Gorilla. The metapophyses (m) continue more distinct and prominent. 
When naturally articulated together, they form a straight line, without any tendency 
to convexity forwards as in Man; and the whole series of true vertebre in the Gorilla 
form but one curvature which is slightly concave forwards, especially in the dorsal region. 
In the first lumbar vertebra (Pl. XXXV. fig. 1, |) the metapophysis (m) is still large 
and distinct ; the upper zygapophysis becomes more convex and oblique in position ; the 
