Il6 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 



in low relief; the piliferous pits are arranged in two concentric circles and 

 are much more conspicuous than those of the carapace, and the whole 

 surface of the plate is relatively smooth and finely pitted ; the small supra- 

 orbital scutes are finely punctate, without definite pattern. 



The fragments of the head-shield which Lydekker has figured as belong- 

 ing to this genus ('94, PI. XXX, figs. 2, 3), are incorrectly assigned, 

 most of them being referable to Eucinepeltus* 



The carapace (Plates XVII, XVIII) is remarkably variable, but it 

 remains to be determined how far this variability is individual and how 

 far specific. Much the most complete carapace that I have seen is the one 

 figured on Plate XVII, which was collected by Mr. Brown for the Ameri- 

 can Museum of Natural History and was found in association with a con- 

 siderable part of the skeleton, including a skull of very unusual type. In 

 its form and proportions this carapace is quite similar to that of Glyptodon, 

 but the pattern of ornamentation is more like that of Sclerocalyptus. The 

 carapace is made up of twenty-seven transverse bands of plates, counted 

 along the ventral margin, but not more than nineteen or twenty in the 

 median dorsal line. The anterior opening has its sides extended con- 

 siderably farther forward than its top, and its margin is, of course, formed 

 by the first row of plates ; this row, which is not seen in the figure, being 

 turned in toward the opening, is composed of very small plates, the 

 smallest in the carapace, and they are ornamented merely by the central 

 oval, with its bounding groove, the peripherals being entirely absent or 

 extremely small. The lateral projections are formed by the bifurcation of 

 the first, second and fourth rows of plates, so that the first movable band, 

 which is the tenth row along the margin, becomes continuous with the 

 seventh row near the median dorsal line. The other additional rows of 

 the sides of the carapace are produced by the bifurcation of two bands near 

 the hinder end. On the sides of the carapace are two movable bands of 

 imbricating scutes, which extend upward for rather more than one third 

 of the vertical height of the shell ; the posterior border of the ninth fixed 

 row is bevelled and extends over the tenth, while the anterior border of 

 the twelfth row is likewise bevelled and overlapped by the second movable 

 band. There is much variation in the number of these movable bands ; 

 in the specimen described by Lydekker ('94, p. 47) there are three such 

 bands, while a carapace in the Princeton collection (No. 15,512, Plate 

 XVIII) has three on one side and none at all on the other. 



