This species is represented in the Amherst Collection by five more or less complete skulls, and over twenty jaws, being by far the commonest fossil of the Deseado beds on the Chico del Chubut River, west of Puerto Visser. As mentioned above, there are two types, the first, with larger canines and heavier mandibles, designated by Ameghino as _L. gaudryi_, which I consider males; second, those with smaller canines, and lighter mandibles, slightly smaller in size, which Ameghino designated _L. oxyrhynca_ and I consider females. Practically all of the other species are based on mandibular symphyses varying in details from the above, but in no case sufficiently for me to see a specific variation. The general features have been discussed under the generic description. Incisor 1 has a long crown and a long root, and is greatly crowded by the tushes. Incisor 3 and pm. 1 have the same crowded appearance. In giving the measurements I have used a skull which is typically _L. gaudryi_, a male, and parallel to it have put another skull, which is typically _L. oxyrhynca_, the female. By comparing the two sets of figures, the shortening, of which Ameghino speaks, will be seen to be all in the region of the tushes. SPECIMEN SPECIMEN 3290 3291X MALE FEMALE Upper dentition, length from inc. 1 to m. 3 227 mm. Upper dentition, length from pm. 1 to m. 3 180 mm. Incisor 1, length 12 mm. Incisor 2, length 25 mm. Incisor 3, length 11 mm. Canine, length 12 mm. Premolar 1, length 12 mm. Premolar 1, width 18 mm. Premolar 2, length 18 mm. Premolar 2, width 28 mm. Premolar 3, length 20 mm. Premolar 3, width 34 mm. Premolar 4, length 22 mm. 20 mm. Premolar 4, width 38 mm. 34 mm. Molar 1, length 28 mm. 24 mm. Molar 1, width 40 mm. 38 mm. Molar 2, length 36 mm. 33 mm. Molar 2, width 48 mm. 45 mm. Molar 3, length 46 mm. 46 mm. Molar 3, width 48 mm. 47 mm.