PROFESSOR OWEN ON THE MEGATHERIUM. 
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PLATE XXni. 
Fig. 1. The five sacral vertebrae, upper view. 
Fig. 2. The five sacral vertebrae, back view. 
One-fourth natural size ; c, centrum ; n i, n 4, coalesced neurapophyses ; ns i, 
ns 4, coalesced neural spines, of the four anterior vertebrae ; ns s, neural 
spine of fifth vertebra ; di, 2 , s, 4, 5, diapophyses ; ni i-m 5, metapophyses ; 
o 1-0 5, posterior outlets of nerve-canals ; z, anterior, 2 ', posterior, zygapo- 
physes. 
PLATE XXIV. 
Fig. 1. The second caudal vertebra, back view. 
Fig. 2. The second caudal vertebra, under view, minus the haemal arch. 
Fig. 3. The eleventh caudal vertebra, back view. 
Fig. 4. The eleventh caudal vertebra, side view. 
Fig. 5. The eleventh caudal vertebra, upper view. 
Fig. 6. The eleventh caudal vertebra, under view, minus the haemal arch. 
Fig. 7- The thirteenth caudal vertebra, upper view. 
Fig. 8. The sixteenth caudal vertebra, upper view. 
Fig. 9. The sixteenth caudal vertebra, under view. 
Fig. 10. The seventeenth caudal vertebra, upper view. 
Fig. 11. The seventeenth caudal vertebra, under view. 
Fig. 12. The eighteenth caudal vertebra, back view. 
Fig. 13. The eighteenth caudal vertebra, front view. 
One-fourth natural size ; c, centrum ; hy, anterior, hy\ posterior hypapo- 
physes ; A', their haemal articular surface; n, neural arch and neurapo- 
physes ; ns, neural spine ; d, diapophysis ; pi, pleurapophysis ; m, met- 
apophysis ; 2 , anterior, z' , posterior zygapophysis ; h, haemal arch, hi/, 
(fig. 1) its anterior hypapophysial articular surface, hy”, its posterior hyp- 
apophysial surface ; hs, hmmal spine. 
PLATE XXV. 
Fig. 1. First dorsal rib. 
Fig. 2. Second dorsal rib. 
Fig. 3. Third dorsal rib ; one-fourth natural size. 
Figs. \a, 2a, 3a, their upper articulations. 
Figs. \h, 2h, Sb, their lower articulations; one-half natural size. 
c", articular surface on the head for the centrum ; n”, articular surface on 
the neck for the neurapophysis ; d”, articular surface on the tubercle for 
the diapophysis ; s', anterior condyle for sternum, s”, posterior condyle 
for sternum ; pi, pleurapophysial part, h, haemapophysial part, of rib. 
