FOSSIL MAMMALIA. 107 



large as the Glyptodon clavipes; but the pattern differs in the greater equality of 

 size of the component tessera. The thickness of the largest fragment is one 

 inch and a half, the tessera? vary in -diameter from one inch to half an inch, and 

 are separated by grooves about two lines in depth, and two in diameter. The 

 pattern formed by the anastomosis of these grooves is an irregular net-work ; the 

 contour of the tesserae is either unevenly subcircular, hexagonal, pentagonal, 

 or even four-sided ; with the sides more or less unequal. In those portions of 

 this armour, where one of the tesserae exceeds the contiguous ones in size, the 

 imagination may readily conceive it to be the centre of a rosette, around which . 

 the smaller ones arrange themselves, but there is no regular system of rosettes, 

 as in the portions of the dermal armour of the Glyptodon figured by Weiss, 

 and those brought to England by Sir Woodbine Parish, in which the Central 

 piece is double the size of the marginal ones. 



The portions of the tesselated bony dermal coveringof aDasypodoid quadruped, 

 figured in PI. XXXII. figs. 5 and 4, of the natural size, were discovered folded 

 round the middle and ungueal phalanges, figs. 2 and 3, at Punta Alta, in 

 Bahia Blanca, in an earthy bed interstratified with the conglomerate containing 

 the remains of the fossil Edentals. 



In one of these fragments, measuring six inches long by five broad, the tesserae 

 are arranged in rosettes, and so closely correspond in size and pattern with the 

 bony armour described by M. Lund, as characterizing his species, Hoplophorus 

 euphractus, that I feel no hesitation in referring them to that animal. One of the 

 pattern rosettes is figured at fig. 4, together with the thickness of the armour at 

 this part, and the coarse tubulo-cellular structure of the bone. Another portion 

 of dermal armoUr from the same locality, gives the pattern shown in fig. 5, formed 

 by square or pentagonal tesserae, arranged in transverse rows ; it is certain that 

 this portion of armour belonged to the same animal as the preceding piece ; and 

 probably that it constituted part of the transverse dorsal bands of the Hoplophorus. 



The middle and ungueal phalanx, as well as the portions of armour, are given 

 of the natural size, in PI. XXXII. The upper and outer surface of the phalanx, 

 is shown in fig. 2. It is smooth and flat ; joins the inner surface by a sharp edge, 

 which runs along the upper and inner side of the bone ; and passes by a gradual 

 convexity to the under surface ; the ridge corresponding with the base of the claw, 

 is feebly developed at the under and lateral parts of the base of the claw. Below 

 the double trochlear joint for the middle phalanx, there are two articular surfaces 

 for two large sesamoid bones. 



The middle phalanx corresponds in its small antero-posterior diameter and 

 wedge-shape, with that of the great Glyptodon : but the terminal phalanx is longer 

 and deeper, in proportion to its breadth. 



p 2 



