18:;;).] l"'^ [Cope. 



Ijrolonged ; tlie curve of the tooth is in one plane, and the depth is about 

 equal to the ^Yidth. A narrow fold of the enamel embraces the anterior 

 border of the inner and outer faces ; it is folded back at a right angle 

 within and with a truncate angle without. The enamel is sculptured into 

 numerous close, fine longitudinal grooves, which do not inosculate. The 

 separating ridges number 14 near the middle of the tooth, those near the 

 borders being the strongest. One, strongest of all, is on the external 

 turn of the enamel, and near it numerous interrupted ridges have a slightly 

 oblique direction. 



The incisors are, as in the modern representatives of the Amblyrhiza, 

 of more slender proportions than in the beavers, Arctomys, and other 

 rodents, and their extinct predecessors. They are, also, relatively 

 less stout than those of the Castoroides. Their sculpture is quite similar 

 to that seen in the Lagidium and other chinchillas. 



Lines. 



"Width anteriorly 6. 



Depth 5.7 



Having requested Dr. Rijgersma to make further search in the locali- 

 ties where the preceding specimens were obtained, that gentleman made 

 a sjjecial trip to Anguilla, and made a successful search among the debris 

 and in the caves, whence the supposed phosphatic earth had been exca- 

 vated. He found a considerable number of bones and five additional 

 molars of Amblyrhiza ; also seven molars referred below to a distinct and 

 allied genus (Loxomylus Cope) with numerous incisor teeth belonging to 

 both genera. 



Two adjacent molars of the first named, are in excellent preservation, 

 and the posterior displays one dentinal column more than any other 

 tooth ; it is, therefore, probably the posterior superior. They all display 

 the curved shank and plane crown and contracted root already described. 

 A portion of a superior incisor measures l.Spmm. in transverse diameter, 

 and 1.4 mm. in depth. 



A distal phalange (figured) displays clearly the subungulate character 

 of the genus, in its straight shaft and depressed, truncate extremity. It 

 was found with a few of the teeth and other bones of this species, which 

 are distinguished from the others by their bright red color. 



On a third examination of the locality Dr. Rijgersma found some 

 masses of breccia, in one of which is enclosed a very fine superior incisor 

 of the left side, probably belonging to this species. Both extremities are 

 broken oft', but the remaining fragment measures 7 in. 5 lin. in length; 

 the width of the anterior or enamel covered face is nearly eight lines, and 

 the depth eleven lines; the latter measurement somewhat increased by the 

 partial crushing of the shaft. The enamel exhibits the usual longitudi- 

 nal ridges, but there are two stronger a little within the external margin, 

 and another strongly marked, a quarter inch within the inner margin. 

 This tooth indicates an animal as lai-ge as the largest known Castoroides, 

 for though the incisors of some of the latter slightly exceed those of the 

 present animal, these teeth have a larger proportion to the general bulk 

 in Castoroides than in Amblyrhiza. 



