June 5, 1903.] 



SCIENCE. 



903 



touching one another, though in this region 

 they are not imbricating. The cephalic 

 shield is usually composed of numerous 

 small, non-imbricating, irregularly poly- 

 gonal and rather heavy plates, which are 

 finely pitted, but display no regular 

 sculptural pattern, but in the altogether 

 exceptional genus Peltephilus these plates 

 are large, very thick and coarsely sculp- 

 tured. A further remarkable peculiarity 

 ■of the head-shield in this genus is the pres- 

 ence of one or two pairs of pointed, horn- 

 like scutes upon the rostrum. It is a 

 curious fact that no plates of the tail- 

 sheath have been found in association with 

 any of the genera, except Peltephilus. It 

 seems most unlikely that aU the other 

 genera had unarmored tails, and yet, in 

 view of the large number of well-preserved 

 •specimens, including the caudal vertebrse, 

 that have been collected, it is possible that 

 ■such may have been the case. 



Considerable variety is displayed in the 

 ■dentition, though in no species has any 

 trace of enamel or of the milk-teeth been 

 ■observed. The marked diphyodontism of 

 the modern Tatu makes this fact somewhat 

 ;surprising. Premaxillary teeth and the 

 corresponding mandibular teeth occur in 

 two genera, Proeutatus and Peltephilus, 

 and in the latter they are so closely ap- 

 proximated that the teeth of both upper 

 .and lower jaws form a continuous series. 

 .Prozaedius and Stenotatus have teeth like 

 those of most recent armadillos, while in 

 .Proeutatus the teeth show an incipient 

 •division into lobes and have a complex 

 masticating surface, produced by layers of 

 ■dentine of different hardness and color, 

 and with some resemblance to the teeth of 

 the glyptodonts. In Peltephilus the teeth 

 are sharply pointed and form what ap- 

 pears to have been a formidable lacerating 

 ■ apparatus, while, finally, in Stegothenum 



the dentition is in such an extreme state 

 of reduction that the animal must have 

 been functionally all but edentulous. 



In all the known genera, except Pelte- 

 philus, the skull has a very elongate and 

 usually a slender rostrum, and, with the 

 same exception, the zygomatic arch has a 

 prominent descending, suborbital process, 

 Avhich is generally from the jugal, but 

 sometimes from the zygomatic process of 

 the maxillary also. 



The cervical vertebras closely resemble 

 those of the modern armadillos, one or two 

 vertebrse coalescing with the axis. The 

 trunk is short, and in those genera in which 

 the number is known does not contain more 

 than eleven thoracic and four lumbar 

 vertebrEe; in the lumbar and the posterior 

 part of the thoracic regions the vertebrae 

 have the same complex mode of articula- 

 tion, by means of accessory zygapophyses, 

 as is found in recent genera. The sacrum 

 is long and always has an extensive union 

 with the ischia. The tail varies consid- 

 erably in the different genera; it is 

 usually quite elongated, but in some of the 

 genera, as Proeutatus, it is of only mod- 

 erate length, though very heavy ; in Stego- 

 therium the caudal vertebra are remark- 

 able for the great development of their 

 transverse process. The ribs, both costal 

 and sternal, and the sternum, differ in no 

 important respect from those of the recent 

 armadillos. 



The shoulder-girdle is practically the 

 same as in the existing genera, but the 

 humerus is noteworthy for the great size 

 and prominence of the deltoid ridge, and 

 the epicondylar foramen is always pres- 

 ent. The ulna has a very large olecranon, 

 which in most of the species terminates 

 proximally in a prominent, incurved hook. 

 The manus is always pentadaetyl and all 

 the digits bear claws ; in all known species 



