. The Deseado formation of Patagonia . usps, closely set near the median line, with an incipientcusp on the inner face of the large anterior cusp. Theposterior part of this tooth is arranged as a typical talonid,with one internal and two external cusps on the margin ofa shallow inclosed basin. On the rear of the tooth is asmall crescent-like cingulum, which occurs in the same placeon molars i and 2, but is lacking on molar 3. This is acharacteristic feature of the genus. On the anterior partof the molars is developed a sort of trigonid of small size,and the cusps are indistinct. The posterior
. The Deseado formation of Patagonia . usps, closely set near the median line, with an incipientcusp on the inner face of the large anterior cusp. Theposterior part of this tooth is arranged as a typical talonid,with one internal and two external cusps on the margin ofa shallow inclosed basin. On the rear of the tooth is asmall crescent-like cingulum, which occurs in the same placeon molars i and 2, but is lacking on molar 3. This is acharacteristic feature of the genus. On the anterior partof the molars is developed a sort of trigonid of small size,and the cusps are indistinct. The posterior portion of eachmolar is a large talonid with a shallow basin siuTounded bya low wall on which are three tiny cups (the entoconid,hypoconid, and hypoconulid). Pilchenia lucina Ameghino I^. luciiui Aiiiegl)., 1903, Anal. Mus. Nac. B. A., ser. 3, t. 2, p. , lucina Aniegh., 1904, Anal. Soc. Cienc. Rep. Argen., t. 58, p. 259. In the Deseado l)eds, on the Chico del Chubut River,west of Puerto Visser, we found a single specimen (jf this. Fig. 146. Left mandible willi premolar 3 to molar 4—4 timesnatural size. species which agrees with the single tooth figured Ijy Ameg-hino as the type, and which I interpret as molar 3. Thedescription is given under the genus, the measurementsarc as follows: CALLOMENUS 223 Specimen No. 3110 Lower dentition, dislancc from premolar 3 to molar 3 14 mm. Lower dentition, premolar 3, length 2 mm., width .75 mm. Lower dentition, [)remolar 4, length 5 mm., width mm. Lower dentition, molar i, length 3 mm., width 2 mm. Lower dentition, molar 2, length mm., width 2 mm. Lower dentition, molar 3, length 2 mm., width 1-75 nim. Lower dentition, height under pm. 4 5 mm. Callomenus Amcghino Callomenus Amegh., 1S91, Ncuvos Rcstos Mamif. Fos. Patagonia Austral, p. Sinclair, 1901-6 IVinceton Patag. Expeditions, vol. 4, p. 434. This genus has not been previously reported from theDeseado beds, but we found a tiny lower jaw with threeteeth to rep
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