18 



BULLETIN 110, UNITED STATES NATIONAL MUSEUM. 



united on the inside by a loose suture with the nasals and posteriorly with the 

 prefrontals. 



A moderately wide inferior process with an expanded distal extremity descends 

 to meet the jugal and maxillary. 



The greatest height of the lachrymal of the right side is 254 mm.; greatest 

 length antero-posteriorly is 194 mm. Both elements of specimen No. 4734, 

 U.S.N.M., are present, though found disarticulated. 



Nasals (n.).- — The nasals in Antrodemus are narrow, elongate, bones. In speci- 

 men No. 4734, U.S.N.M., measuring 360 mm. in length. Viewed from above, 

 they gradually increase in width posteriorly. Both nasal bones were found dis- 

 articulated with this specimen, and though slightly distorted by pressure are other- 

 wise perfectly preserved. 



A'^^ 



Fig. 9.— Left NASAL OF Antrodemus VALENs Leidt. No. 4734, U.S.N.M. * nat. size. (A) Lateral view; (B) ventral 

 \^EW; a, nasal contribution to the boundary of the anterior nabes; la, surface joining lachrymal; p.fr, sueface 

 JOINING prefrontal; pmi, notch receiving peemaxillary process. 



They unite along their whole length on the midline by a deep vertical suture, 

 the opposing surfaces of which are comparatively smooth. 



Posteriorly the nasals are thin dorso-ventrally, but thicken anteriorly, reaching 

 their maximum diameter just posterior to the border of the external nares. On the 

 ventral side of the posterior end, where they overlap the forward ends of the f rentals, 

 these bones are longitudinally grooved with intervening ridges. (See B, fig. 9.) 



On the external side at a pomt about one-third the total length of the bone from 

 the posterior end is a slender spurlike process (fig. 9, la) that extends backward and 

 slightly outward from the border and in the articulated skull passed on the outside 

 of the anterior branch of the lachrjTnal as shown in figure 1. The external surface 

 forward of this spur drops abruptly downward at right angles to the superior sur- 

 face, presenting a sharp, raised edge where the two surfaces meet. 



The narrow anterior end is bifurcated dorso-ventrally, the superior process 

 from the premaxillary being received in a cleft in the dorsal prolongation (fig. 9). 



