Cope.] '^"'-' [April 15, 



species does not belong to HyracTiyus. The anterior cross-crest of the 

 molar preserved, is lobate, resembling the same ridge in the species of An- 

 cMtJierium. The posterior cross-crest is uninterrupted. If this species 

 possesses affinity with AncMtliermm, it Avill perhaps possess three digits of 

 the manus, in which case it will be referred to the Triplopidce, in harmony 

 with the indication furnished by the ear structure. 



The Triplopus amarorum is much larger than the T. cuMtalis, equalling^ 

 the Hyracodon nebrascensis. It differs from the T. eubitalis in the stronger 

 temporal ridges, and more elevated sagittal crest ; also, in the shorter post- 

 tympanic process. The internal lobes of the last superior molar are con- 

 nected by a basal ledge, not found in the T. eubitalis. 



The interorbital space is wide and flat, and is most expanded at the post- 

 orbital angles. 



From this point the face contracts rapidly forwards. From the same 

 angle it contracts abruptly posteriorly to the rather narrow brain-case. 

 The anterior temporal ridges are nearly transverse near the postorbital 

 processes, and then converge more gradually, uniting opposite the posterior 

 inferior border of the zygomatic fossa. The elevated sagittal crest diverges 

 into two lateral supraoccipital crests, which contract as they descend, and 

 continue to the extremities of the posttympanic processes. Although the 

 postorbital angles are prominent, they cannot be called processes. The 

 paroccipital processes are large, and are directed vertically downwards. 

 They are separated by the usual concavity from the occipital condyles. 

 The posttympanics are very short, forming only an angle projecting 

 downwards at the anterior base of the paroccipitals, from which they 

 are only separated by a notch. The inferior side of the tympanic bone 

 is fiat near the meatus, but opposite the stylomastoid fossa its posterior 

 border is turned forwards, and is produced into a well marked process. It 

 encloses a groove in' front of it, which is continuous with the pterygoid 

 fossa. The petrous bone is not inflated, and its inferior surface is divided 

 into two longitudinal ridges. The inner is the less prominent, and is in 

 close contact with the basioccipital. The postglenoid processes are robust 

 and obtuse. The basioccipital is excavated in front of each of the con- 

 dyles. The inferior surface is nearly flat, with a slight median keel. The 

 pterygoid fossa is well defined, and is long and narrow. The posterior nareal 

 trough is elohgate, the descending pterygoid processes of the sphenoid 

 originating as far back as the apex of the os petrosum. This species is es- 

 pecially characterized by the presence of an acute keel-like ridge, which 

 extends horizontally above the foramina sphenoorbitale and opticum, and 

 turns upwards anterior to the latter, terminating a half inch below the in- 

 ferior base of the postorbital process. All the foramina are below it, but 

 there is a fossa above it, opposite the interspace between the/, opticum and 

 /. s'plienoorbitale. 



A supraorbital foramen pierces the frontal bone, a quarter of an inch 

 within the superciliary border. There are five or six postparietal foramina, 

 two of which are nearly on the squamosal suture. There is a postsqua- 



