INSECTIVORA OF THE SANTA CRUZ BEDS. 371 



axis is so provided. In neither Chrysochloris nor Necrolestes are the 

 cervicals at all like the curiously reduced and ankylosed neck vertebrae 

 of Notoryctes. 



The thoracic vertebrae also are like those of Chrysochloris, with small, 

 subcylindrical centra, broad, depressed neural arches, and short neural 

 spines, which, as in the African genus, all incline backward, there being 

 no anticlinal vertebra. The spines and metapophyses are, at least in the 

 posterior half of the region, somewhat better developed than in Chryso- 

 chloris, as is also true of Notoryctes, though in the latter the spines are 

 much more slender than in either of the insectivorous genera. 



The lumbar vertebrae number at least four and perhaps five. The centra 

 are broad and depressed, and the neural spines are quite elongated and 

 are directed obliquely backward, as in the African form. The spines are 

 somewhat longer than in the latter and have less of a rectangular shape, 

 their free ends being more curved and pointed and less abruptly truncated. 

 The metapophyses also are more prominent, and the transverse processes, 

 though nearly as much reduced in size, are further removed from them, 

 arising from the centra and not from the arches. In Notoryctes the lum- 

 bars are quite different from those of either of the other genera ; the first 

 one is the anticlinal, with an erect spine, while the spines of the others 

 incline forward. The spines also are much smaller and more slender 

 than in the two insectivores ; the transverse processes, on the other hand, 

 are much better developed, as are also the metapophyses, and the zyga- 

 pophyses are of the interlocking cylindrical type. A remnant of the latter 

 structure is observable in Necrolestes. 



The sacrum is very like that of Chrysochloris. Dobson gives the num- 

 ber of sacral vertebrae in the latter as five, but of these only three are true 

 sacrals and are in contact with the ilium. In Necrolestes the arrangement 

 is the same except that the two succeeding vertebrae, which in the recent 

 genus are fused with the sacrum, are free and separate. The centra of the 

 sacral vertebrae are broader and heavier than in the African type and the 

 neural spines are even more reduced, not uniting into a continuous ridge. 

 The iliac surface is large. Notoryctes has a very peculiar sacrum, quite 

 different from that of the other two genera ; it is very long and broad and on 

 each side the transverse processes unite into a bony plate which is con- 

 nected in front with the ilium and behind with the ischium, while ventral 

 transverse processes (pleurapophyses ?) from the last two vertebrae are 



