Cope.] l\)^ [£)ec. 16, 



eratel}' stout. The enamel of the first incisor does not extend below the 

 alveolar border, at the internal and external faces, and does not reach it at 

 the sides. It has a few wrinkles on the anterior face. The anterior enamel 

 face of the second incisor is thrown into shallow longitudinal grooves with 

 more or less numerous irregularities from the low dividing ridges. There 

 is a deeper groove on each side of the tooth, and there are about a dozen 

 ridges between these on the anterior face. Both cusps of the first pre- 

 molar are conic, and the external is the larger. The second true molar 

 is a little smaller than the first. The enamel of the premolars and molars 

 is smooth, and there are no cingula. 



Probable length of dental series, .0750; diameters of I. i : anteropos- 

 terior, .0120, transverse, .0066 ; diameters I. 2 : anteroposterior, .0160, 

 ti'ansverse, .0115 ; diameters P-m. i : anteroposterior, .0072 ; transverse, 

 .0130 ; diameters of M. ii , anteroposterior, .0090, transverse, .0090. 

 Length of true molars, .0038 ; depth of ramus at M. ii, .0360. 



The short deep jaws of this animal must have given it a very peculiar 

 appearance, not unlike that of a parrot in outline. 



PSITTACOTHERIUM ASPASI^, Sp. UOV. 



Represented by two mandibular rami of two individuals, one adult, the 

 other nearly so, but with the last inferior molar not fully protruded. The 

 latter specimen must be used for description, as it presents two molar 

 teeth, while the other specimen has lost them. 



The most obvious difference from the P. multifrcujiim is its inferior size, 

 which can be readily perceived from the measurements given. The pos- 

 terior crest of the molars appears to have less transverse extent than in 

 the larger species. This crest in the last inferior molar has a curved 

 crenate edge, with a small conic tubercle at its external extremity. The 

 anterior crest consists of two conic tubercles, whose apices converge, but 

 whose bases are closely appressed, and only diatinguished by a superficial 

 fissure. The valley between the crests is uninterrupted. The preceding 

 molar is larger, and its posterior crest is like that of the lost molar. The 

 apex of the anterior crest is broken ofli". 



The ramus deepens rapidly forwards, and contains the enormous alve- 

 olus for the incisors. The coronoid process leaves the alveolar border at 

 the line separating the last two molars, or, in the smaller specimen, a 

 little anterior to this point, and is quite prominent. The masseteric 'fossa 

 is well marked, but shallows gradually anteriorly and inferiorly. 

 Measurements. 



No. 1. M. 



Depth of ramus at penultimate molar 027 



Width of last molar anteriorly 008 



Length of crown of do 009 



No. 2. 



Depth of ramus of jienultimate molar 029 



at P-m. ii 043 



Length of five consecutive alveoli 047 



From the Puerco bed of N. W. New Mexico. 



