EDENTATA OF THE SANTA CRUZ BEDS. 189 



Though several thoracic vertebrae have been lost from this skeleton, 

 other species of the same genus indicate that the number was twenty-one 

 or twenty-two. In the anterior part of the thorax the vertebrae have small 

 centra, very broad neural arches and short, heavy spines, which incline 

 backward, are thickened and rugose at the free ends, and so broad that 

 hardly any intervals appear between the successive spines. The contrast 

 in length between these short spines and the elongate processes of the 

 great Pampean genera is very striking. Posteriorly, the centra become 

 larger, especially in width, and on the ventral side of the penultimate 

 thoracic are two small foramina, which on the last one become large and 

 conspicuous ; the transverse processes gradually shorten and have a more 

 elevated position, arising from the neural arch rather than the centrum ; 

 the neural spines are somewhat shorter and less inclined, but broader and 

 thicker. The accessory articular processes are not very well preserved, 

 but seem to agree perfectly with those of other species of Hapalops and 

 to consist of only one additional pair each of pre- and of post-zyga- 

 pophyses. 



In this individual are three lumbar vertebrae, which closely resemble 

 the last two or three thoracics, but are larger ; the centra are very broad 

 and depressed, increasing in width posteriorly. The ventral foramina are 

 very conspicuous, though this was a rather aged animal, with epiphyses 

 united to the centra. The neural spines are broad and much thickened 

 at the tip, but short and nearly erect ; the transverse processes are rather 

 short, but very broad, depressed, plate-like and curved forward. 



Apparently the sacrum consists of six vertebrae, of which the first may 

 be a lumbar, for its centrum is still separate from the others, though the 

 spine is fused with the common ridge. In the middle part of the sacrum 

 the centra become very thin and depressed, increasing again in thickness 

 posteriorly. The ilia articulate with the first three, or perhaps, four ver- 

 tebrae and the ischia with the last two. 



Of the caudal vertebrae, nine are preserved, the first four in their natural 

 position. Evidently, the tail was very stout, but not very long, and the 

 number of vertebrae was probably not much more or less than twenty. 

 The first caudal is large and massive and might easily be mistaken for 

 the lumbar of a smaller animal ; the centrum is short, broad and somewhat 

 depressed, with transversely oval, nearly plane faces, and on the ventral 

 side two parallel ridges, which bear facets for the first chevron-bone ; the 



