f EDENTATA OF THE SANTA CRUZ BEDS. 13 



scutes of the carapace, of quite peculiar type. In a subsequent publica- 

 tion ('94) the former was referred to the Monotremata, while the latter 

 was regarded as most nearly allied to Peltepkilus. Until the collections 

 made by Messrs. Hatcher and Peterson, no additional specimens of these 

 extraordinary animals, other than scattered plates of the carapace, had 

 been obtained. On examining the drawings and notes which I had taken 

 with me to La Plata, Dr. Ameghino at once expressed the belief that these 

 two supposedly different genera were really one and the same, a belief 

 which has been abundantly confirmed by the material in the Princeton 

 collection. In his last paper on the subject ('02, p. 65) the original de- 

 scriber has formally retained the name Stegotherimn and treated Scotceops 

 as a synonym. 



In the Princeton collection the genus is represented by two specimens 

 which seem referable to S. tesselatum, for though they may possibly rep- 

 resent two different species, the differences between them are more prob- 

 ably due to individual variation. Of these specimens, one (No. 15,566) 

 comprises the greater part of the carapace, about half of the skull, the atlas, 

 the compound cervical, seven thoracic and four lumbar vertebrae, the 

 sacrum and all of the caudal vertebras, save the three or four terminal 

 ones, together with two ribs, the scapula, humerus, pelvis, femur, tibia and 

 fibula. The second specimen (No. 15,565) has the anterior portion of the 

 carapace, the skull complete, the neck except the sixth and seventh cervi- 

 cals, two thoracic vertebras, and the right pes. 



Carapace. The carapace differs quite markedly from that of any other 

 known Santa Cruz genus. I am unable to say whether a pelvic buckler 

 was formed or not, but it is clear that there was no anterior buckler, and in 

 one of the specimens twenty movable bands may be counted in position 

 (Plate I). In the anterior region the scutes are smaller and thicker, and 

 their exposed portions have a more nearly square outline than those of 

 the middle region ; in longitudinal section these scutes are lozenge-shaped, 

 with long diameter in the fore-and-aft direction and with no notable dif- 

 ference in thickness between the exposed and covered portions of the 

 plates. Indeed, in this region there is but a partial imbrication of the 

 plates and the mobility of the bands must have been relatively slight ; 

 only a small change in the character of the plates would be needed to 

 convert this portion of the carapace into a fixed scapular shield. In the 

 middle region of the carapace the plates are much elongated, becoming 



