OSTEOLOGY OF CAENIVOROUS DINOSAURS. 



11 



Fig. 4.— SkULLOFANTRODEM VALENSLIEDV. POSTEKIOB VIEW. NO. 

 4734, U.S.N. M. i NAT. SIZE. 6. or, BASIOCCIPITAL; 6. 5, basisfhenoid; 



b. pt. pr, basisipteeygoid processes of the basisphenoid; ex. oc, 

 exoccipital; pa, parietal; p. oc, paraoccipital process; po. /, 



POSTFKONTAL; S. OC, SUPRAOCCIPITAL; Sq, SQUAMOSAL. 



allTdirections, such as would be naturally expected in an animal of carnivorous 

 habits. The condyle as in nearly all dinosaurs is inclined vontrally in relation to the 

 longer horizontal axis of the skull. 



The median superior surface of the ^^' 



basioccipital contributes to the m- 

 ferior boundary of the foramen 

 magnum, much as in Campto- 

 saurus but to a slightly less de- 

 gree. 



The ventral process extends 

 downward some 57 millimeters be- 

 low the occipital condyle. It is 

 comparatively narrow and articu- 

 lates laterally with the ventral 

 processes of the exoccipitals, as 

 well as the posteriorly directed 

 plates of the basisphenoid. The 

 median posterior and ventral sur- 

 faces are deeply concave thus sepa- 

 ratmg the subspatulate basioccipi- 

 tal processes, see figure 4. 



Exoccipital (ex. oc.) and para- 

 occipital ip. oc). — The exoccipitals 

 seen from behind extend outward from the basioccipital in two broad wing-like plates 

 with which the paraoccipitals are coalesced. It can not be determined from the 



present specimen whether they meet on 

 ^,? the median line above the foramen mag- 



num or not, but I am inclined to be- 

 lieve that thesupraoccipitalisnot inter- 

 posed between them. The paraoccipital 

 processes extend outward, backw-ard, 

 and downward at an angle of 45° to 

 the central surface terminating at a line 

 40 mm. posterior to the rear of the oc- 

 cipital condyle. The upper and lower 

 borders of these processes gradually ap- 

 proach one another toward their outer 

 extremities which are obliquely trun- 

 cated. Dorsally the exoccipitals and 

 paraoccipitals unite in order from the 

 center outwards with supraoccipitals, 

 parietals and squamosals, the latter 

 being applied more to the upper ante- 

 rior face of the paraoccipital than to 

 the dorsal border. On the anterior 

 median surface these coalesced bones unite by a long lapping suture with the pro- 

 otics (fio-. 6). The elongated aperture between the paraoccipital and squamosal in 



Fig. 3.— Skull of Antrodemus valens Leidy. No. 4734, U.S. 

 N.M. i NAT. size. Superior view. al. sp, alisphenoid; /, 

 frontal; n. s, sutural surface for nasal bones; pa, pa- 

 rietal; p. oc, paraoccipital process; po./, postfrontal; s.f, 

 supratemporal fossa; sq, squamosal. 



