i894. ^^^ LA PLATA MUSEUM. 33 



attachment of the pelvis. The occurrence of this peculiarity in two- 

 examples shows that this feature cannot be an abnormality ; but, 

 unless (as Dr. Moreno thinks) it be glandular, I am quite at a loss to 

 guess its rise or object. The skull in this genus has a straight profile 

 from the occiput to the tip of the nasal bones, in consequence of 

 which the oblong aperture of the nose is of great vertical height. 



In marked contrast to Docdicurus are the plates of the carapace 

 in the allied genus PajwchtJius, which, although oblong in form, have a 

 peculiarly roughened and particular external surface, without perfora- 

 tions for bristles. Occasionally, however, specimens are found 

 showing the impress of horny shields arranged in a rosette-like 

 pattern somewhat after the manner obtaining in Glyptodon. The tail 

 of Panochthus differed from that of Dcedicunis in that the terminal tube 

 was less flattened, and not expanded, while it was covered with 

 granules interspersed with disk-like surfaces, which were prominent 

 instead of depressed, and thus evident^ bore a different type of 

 spine. More striking is the remarkable difference in the form of the 

 skull, which had a highly vaulted profile, narrow, oblique nostrils, 

 and an enormous descending process to the zygomatic arch. One 

 specimen of the skull has its dermal covering of bone still preserved ; 

 each plate consisting of a smooth central disc surrounded by granular 

 bone. Of this gigantic creature, which rivalled Dcedicuvus in bulk, 

 although v.'ith a smaller tail, the Museum possesses in addition to 

 several unmounted specimens, one entire carapace, three complete 

 mounted skeletons, exclusive of the carapace, but with the terminal 

 tail-tube, another lacking the tail, as v/ell as a portion of a fifth. 



In addition to the peculiarities in the structure of the component 

 bony plates of tlie carapace already referred to, Glyptodon differs from 

 both the genera above-mentioned by the form of the tail-sheath, 

 which is composed of a number of rings, gradually decreasing in 

 diameter, and ornamented with a series of conical knobs, the extremity 

 consisting of a short cone similarly decorated ; the similarity of this 

 tail-sheath to that of the extinct Australian tortoise Miolania being 

 not a little remarkable. The skull of this genus has neither the 

 straight profile of Docdicurus nor the convex one of Panochthus, but 

 the frontal and parietal planes meet one another at an obtuse 

 angle, thus causing the nasal aperture to be wider than long. 

 One skull from the Pampean and a second from Monte Hermoso 

 have the bony dermal shield preserved, and show that it was com- 

 posed of small juxtaposed plates, which become larger and imbricating 

 on the occiput. Of the Pampean forms, which apparently belong 

 to two species, the mounted series in the Museum comprises two 

 skeletons and nearly a score of more or less nearly complete carapaces. 

 There is also a fine series of the remains of the smaller species from 

 Monte Hermoso. 



In the genus which we may provisionally allude to under the 

 name of Hoplophorus, the skull, as is well shown in a beautiful 



D 



