372 PATAGONIAN EXPEDITIONS: PAL/EONTOLOGY. 



likewise ankylosed with the ischium. The .sacrum thus appears to be 

 covered with a small carapace. 



One very marked difference between Necrolestes and Chrysochloris is in 

 the character of the tail, which in the latter is very short and rudimentary, 

 but in the former was evidently quite long, stout and well developed. 

 The anterior caudal vertebrae, at least, have complete spines, transverse 

 processes, metapophyses and zygapophyses, which in the African genus 

 are either obsolescent or wanting. On the other hand, the processes are 

 not so long and prominent as they are in Notoryctes, nor have any ver- 

 tebrae at all resembling the curious, massive distal caudals of the marsupial 

 been found in connection with the Patagonian fossils. 



As a whole, the vertebral column is exceedingly like that of Chryso- 

 chloris, but slightly less modified. The various processes and spines are 

 not so much reduced and the tail is considerably longer and better 

 developed. 



The fore-limb is curiously alike in all three of the genera here discussed, 

 though it would seem that Necrolestes had been less completely adapted 

 to a burrowing mode of life than either of the modern genera. 



Of the scapula not enough is preserved to display the form, but what 

 remains resembles the corresponding part of Notoryctes rather than that of 

 Chrysochloris. The postscapular fossa differs from that of the latter in 

 being convex instead of coneave, as is also the case in the marsupial, and 

 the neck is much narrower, and, as in the latter, the ridge which runs 

 parallel with the spine near to the glenoid border is very prominently 

 developed, and curving toward the spine almost forms a tube. This ridge 

 is likewise indicated in Chrysochloris, but is very inconspicuous. The 

 spine is high and recurved and evidently terminated in a long acromion, 

 but whether the latter attained such exaggerated proportions as in the two 

 existing genera, there are no means of determining. The glenoid cavity 

 is a broad oval and quite deeply concave, and the coracoid is obsolete, 

 as it also is in Chrysochloris, while in Notoryctes it is quite well developed. 



The humerus (Plate LXIV, figs. 4-4") is extraordinarily like that of 

 Chrysochloris, with only a few minor differences. The head is large, 

 strongly convex and of ovoid shape, with the long axis directed parallel 

 to that of the shaft ; it is a little smaller but projects rather more behind 

 the plane of the shaft than in the African genus. The tuberosities are also 

 well developed, but the internal one is not so large as in Chrysochloris 



