Darwin's original specimen, on which the genus Glossotherium of Owen was founded, is preserved in the Museum of the Royal College of Surgeons. It has thus been possible to compare it directly with the undoubted cranium of Grypotherium from the Patagonian cavern. The specimen is merely the left half of the hinder part of the cranium, and is therefore very inadequate for discussion; but several features seem worthy of note. Compared with the new skull No. 1, the fragment named Glossotherium has (i.) the inner wall of the temporal fossa less flattened, (ii.) the digastric fossa deeper in proportion to its width, (iii.) the hinder border of the inflated pterygoid vertical, instead of sloping downwards and forwards, (iv.) a much larger and deeper pit for the articulation of the stylohyal, and (v.) a longer canal penetrating the base of the occipital condyle for the passage of the hypoglossal nerve. In all these respects the so-called Glossotherium agrees much more closely with the typical Mylodon; and Owen was probably correct in 1842 when he expressed the opinion that the two are at least generically identical.[52]
I am therefore of opinion that Grypotherium is the correct generic name for the Ground-Sloth from the Patagonian cavern, while Glossotherium must be relegated to the synonymy of Mylodon.
The specific determination of the new specimens is more difficult. As remarked by Roth, only two species of Grypotherium seem to be already known from the Pampa formation—G. darwini by three skulls[53] and G. bonaerense solely by a maxilla.[54] The portions of skull and dentition now under discussion indicate an animal much larger than G. bonaerense (assuming the original maxilla to be that of an adult); while they are considerably smaller than any known specimen of G. darwini. Moreover, the nasal arcade now described is narrower and more concave on its outer face than that of G. darwini, as already observed by Roth. It thus seems very probable that the animal from the Patagonian cavern represents a distinct species, which must bear the name of G. listai. This specific name was given by Ameghino to a fragment of the first-discovered piece of skin, and the curious argument which leads Roth to propose the substitution of a new name for it does not affect its validity.
It may be added that Dr. Erland Nordenskjöld has recently compared his specimens from the Patagonian cavern with the skull of Grypotherium darwini at Copenhagen, and finds no specific difference.[55] No particulars however, have yet been published.
2. Associated Mammalian Remains.
Felis, sp.
A feline carnivore larger than the existing Jaguar (Felis onca), but about the same size as an average Tiger (F. tigris), is represented in the collection by the distal half of a right humerus (No. 44), a left fourth metatarsal (No. 46), and the distal end of another metatarsal (No. 47). These bones have evidently been buried in dust, but are in the same fresh state of preservation as those of Grypotherium.
Careful comparison of these bones shows that they are undoubtedly feline; and there is no difficulty in determining that they belong to Felis rather than to the extinct Machærodus. A humerus of M. neogæus, from a Brazilian cavern, now in the British Museum (No. 18972 b), is readily distinguished from the new Patagonian humerus by the remarkable lateral compression of its shaft and the much greater downward extension of its prominent and sharp deltoid ridge. The humerus in all the large species of Felis, on the other hand, only differs from the fossil now under discussion in very small particulars. In fact, the humerus and metatarsals of the existing Felis onca are essentially identical with the bones from the Patagonian cavern, except that they are rather smaller. I am therefore inclined to regard the newly discovered remains as indicating a comparatively large variety of F. onca, which once lived in the temperate regions of Patagonia, beyond the present range of this species. Such an occurrence would be a precise parallel to that of the Cave-Lion in Europe. It is well known that nearly all the remains of F. leo found in the Pleistocene formations of the temperate parts of the Old World indicate animals of somewhat larger size than any surviving in the warmer regions to which the species is now confined.[56]
It may be noted that bones of the Jaguar of ordinary dimensions have been recorded from the Pampa formation of the Province of Buenos Aires.[57]