DICOTYUNjE OF AMERICA. 329 



5. Lower part of both ossa humeri (lb., plale 4, fig. 21,) of the right side. 



6. Bone of fore arm, (lb., plate 4, fig. 21.) 



7. A right metacarpal, without the distal epiphysis, (lb., figs. 23, 24.) 



8. Two astragali: diameter from the bottom of the tibial to the distal trochlea fourteen lines; transverse dia- 

 meter at middle eight lines. 



9. Fragment of an os calcis. 



The most important specimen, upon which the genus Ilyops was proposed, consists of 

 the upper portion of a cranium and face much fractured, (l'l. 38, Fig. 1). The size of 

 the fragment is such as to indicate the existence of an animal a little larger than the 

 Dicotyles labiatus, but possessing relatively a little shorter and broader forehead, and a 

 longer and broader, but shallower face. The lateral margins of the forehead and the 

 upper part of the inion are broken away, but it appears as if the length of the former 

 had a little exceeded its breadth. The forehead is also a little more depressed on each 

 side. 



The face slopes from the position of the orbito-frontal foramina more abruptly down- 

 wards and forwards than in Dicotyles, and after two inches of its course rather abruptly 

 ceases to incline so much downwards. That portion of the ossa nasi posteriorly and 

 outside of the groove leading from the orbito-frontal foramina is prominently convex, and 

 on a level with their median line. The fronto-nasal suture forms the outline of a de- 

 pressed cone with rounded apex, two and a half inches wide at base, and thirteen lines 

 in depth. Anteriorly the ossa nasi are about as convex transversely as in D. labiatus. 



The orbito-frontal foramina are thirteen lines apart. The upper extremity of the ossa 

 iuter-maxillaria, alone preserved in the specimen, inclines at an angle only of about 35°, 

 and the distance of its point from the suture connecting the nasal process of the superior 

 maxillary bone with the os frbntis, is two inches one and a half lines. The nasal process 

 of the superior maxillary bone slopes from the ossa nasi laterally at an angle of about 35°. 



A prominent acute ridge appears to have existed at the sido of the superior maxillary 

 bones, proceeding forwards from the inferior margin of the malar bone in the existing 

 species of Dicotyles, and more especially like that in D. labiatus, but the specimen is too 

 much mutilated to determine its exact extent and character. 



The anterior extremity of the malar bone is broad, not more depressed than in D. labi- 

 atus, and inclines at about the same angle as the contiguous portion of the superior maxil- 

 lary bone. 



The fractured condition of the specimen permits the extensive sinuses to be seen which 

 every where occupy a position between the tables of the cranial bones, and communicate 

 freely with the ethmoidal and nasal sinuses. 



I rom what has liccn stated in regard to this fragment, it will have been perceived not 

 to possess a single character which would separate the annual from the genus Dicotyles, 

 t" which Dr. Le Contc considered it belonging, subsequently* to its being first ascribed to 

 1 1\ ops. 



* Pr. A. N S vi. 3. 



