OSTEOLOGY OF CARNIVOROUS DINOSAURS. 



29 



First antiorbital fenestra (/"')■ — The first antiorbital fenestra is of large size, 

 being relatively larger than in either Tyrannosaurus or Ceratosaurus and by far 

 the largest vacuity in the skull. Its upper boundary is formed by the lachrymal 

 and maxillary, anteriorly by the maxillary, ventrally by the maxillary and jugal, 

 and posteriorly by the descending branch of the lachrymal. 



Second antiorbital fenestra (f"). — This opening which is small, subcircular in 

 outline lies wholly within the maxillary. 



Anterior nares (ex.nar.). — The external narial opening is elongate, oval. in form 

 and is bounded above by the nasal and premaxillary bones; anteriorly by the pre- 

 maxillary; below by premaxillary and maxillary and posteriorly by the nasal and 

 maxillary. In this specimen it has a length antero-posteriorly of 118 mm.; a depth 

 at the center of about 40 mm. 



Fig. 16.— A, Oblique side view of brain case of Antrodemus valens Leidy, No. 5753, A. M., N. H. | nat. size. B. the 



SAME WITH POSTFEONTAL AND SQUAMOSAL REMOVED; b.pt.pr, BASIPTEYGOID PROCESSES; B.sp, BASISPHENOID; Car. in, 

 CAROTID INTERNUS; COU, OCCIPITAL CONDYLE; /.TO, FORAMEN MAGNUM; fen.OT, FENESTRA OVALIS; Ft, FRONTAL; Op. 0, 



paroccipital; o.sp, alisphenoid; Pa, parietal; Po, postorbital complex; Pr.ot, prootic; P.sp, presphenoid; qu.cot, 



COTYLUS FOR QUADRATE; S.OC, SUPRAOCCIPITAL; Sq, SQUAMOSAL; tub. B.OC, TUBEROSITY OF BASIOCCIPITAL; tub. B.Sp, 

 TUBEROSITY OF BASISPHENOID; I, II, III, IV, V, VII, IX, XI, XII, FORAMINA FOR EXIT OF CRANIAL NERVES. PARAOCCIPITAL 

 REPRESENTED AS TRANSPARENT IN ORDER TO SHOW FORAMINA. BOTH FIGURES (AFTER OSBORN). 



Supratemporal fossa (s.t.f). — The supratemporal fossae are of large size, espe- 

 cially when compared with those of Ceratosaurus nasicornis. Although these vacui- 

 ties are considerably larger than as represented in Marsh's restoration of the top view 

 of the skull of that animal. This fossa in Antrodemus is bounded anteriorly by the 

 frontals, alisphenoid, and postorbitals; externally by the postorbital and squamosal 

 above, below by the prootic and exoccipital; internally by the parietal, prootic 

 and alisphenoid. 



TEETH. 



The dental formula of Antrodemus valens Leidy as shown by a study of several 

 individuals: 



Upper jaw: premaxillary, 5; maxillary, 15 to 17; total, 20 to 22. 

 Lower jaw : Dentary, 15. 



