SKEL-ETON OF QUADRUMANA. 5-25 



obtains in the second (s, answering to the third Human) lumbar 

 vertebra ; the diapophyses are broader and more depressed in the 

 Gorilla ; a fossa divides the anterior zygapophysis from the meta- 

 pophysis ; the centrum is as broad as in Man, but is deeper and 

 longer ; the neural spine extends more obliquely backward, and 

 its expanded apex is bifid. In the third lumbar vertebra, 4, the 

 difference is very striking in the minor expanse of the centrum 

 in the Gorilla, especially behind, in the much smaller and more 

 depressed form of the neural canal, in the shorter and broader 

 diapophysis, the more distinct metapophysis, in the convex an- 

 terior and more approximated posterior zygapophyses, and in the 

 greater length of the centrum. In old males this vertebra is 

 included by the ilia. The whole series of true vertebrae in the 

 Gorilla form but one curvature, which is slightly concave forward, 

 especially in the dorsal region. 



The sacrum departs in a greater and more instructive degree 

 from the Human type ; it consists of five or six anchylosed 

 vertebrae, but they are longer and narrower than in Man, and 

 present a very slight curve, with the concavity forward ; the 

 neural foramina are much smaller, the neural sj^ines much more 

 developed, and coalesce to form a single strong bony ridge, ex- 

 tended over and gradually subsiding on the last sacral vertebra, 

 the neural arch of which is entire ; the first sacral vertebra, ib. 5, 

 answers to the fifth lumbar in Man ; the zygapophyses are 

 smaller, but the metapophyses are present and well developed. 

 The posterior outlets for the sacral nerves are very small, and 

 the whole neural canal is much more contracted than in Man. 



B. The Skull— The skull of the Aye-aye, fig. 343, in com- 

 parison with that of lower mammals of similar size, is remarkable 

 for the large proportion of the cranium to the face, and the 

 extreme shortness of the latter in advance of the orbits. Its 

 profile contour, from the upper border of the foramen magnum, 

 curves rapidly from the occipital to the parietal region, and is 

 continued with a bold convexity to the root of the nose, whence 

 it slopes straight to the nostril. The cranium is still more con- 

 vex transversely ; it expands a little in advance of the lambdoid 

 ridge, and gradually, but very slightly, contracts to the post- 

 orbital processes ; these, meeting with the malars, complete the 

 rim of the orbit, which opens widely beneath that part of the 

 frame into the temporal fossa. 



In the complete circumscription of the rim of the bony orbit 

 Chiromys exemplifies its quadrumanous affinity ; whilst it shows 

 the special family to which in that order it belongs by the 



