-g THE CERATOPSIA 



The rear of the skull exhibits the usual ceratopsian complex— a spherical condyle, heavy basi- 

 occipital region, and two forwardly directed processes which abut against the pterygoids. The 

 pterygoids are typically ceratopsian, but have an immensely greater vertical extent than in the 

 Ceratopsidae. The exoccipitals are widespread but are narrow vertically and do not dilate so much 

 toward their outer end as in the latter. The pterygoid groove is not in evidence as it is in Trkeratops 

 serratus. The suture between the parietals and occipital complex is clear, crossing the vertical ridge 

 above the foramen magnum at its mid-height, as in Monoclonius (Centrosaums). As usual, one 

 cannot determine the limits between the supra- and exoccipitals. 



The lower jaw is extremely hollow and must have possessed a large splenial which is not now 

 in evidence. There is a row of 12 to 13 large nutritive foramina on the inside of the dentary, one 

 at the base of each vertical tooth row, and a corresponding series of 13 to 15 on the inner side of the 

 maxillary. The angular and surangular are large. The coronoid seems to lack the forwardly turned 

 hook-like summit characteristic of later ceratopsians, but is grooved slightly in the direction of the 

 temporal muscle pull. (See above, p. 37.) 



The outer surface of both mandible and maxilla bears ridges limiting the masseter muscle. 

 Between the latter and the teeth were hollows which formed deep but probably not distensible 

 cheek pouches, as Hatcher suggested for Trkeratops. These are merely for the retention of food 

 which, falling outside of the teeth, would otherwise be lost. They were in no sense for storage. 

 Below the masseter ridge the mandible has a flattened outer surface more suggestive of Monoclonius 

 {Centrosaums) than of Trkeratops. The predentary is sharply pointed, with a keel-like profile 

 The shape of the various sutures of skull and jaws varies in the two specimens, No. 6408 and 



No. 6429 A.M.N.H. 



As but one species of Protoceratops is known, it is impossible as yet to determine what are the 

 specific as opposed to the generic characters. 



The generic relationship is nearest to Leptoceratops among the American forms. Ihe 

 distinctions from Brachyceratops are much more marked. (See contrast of Leptoceratops and 

 Brachyceratops, p. 79.) 



Genus LEPTOCERATOPS Brown 



Leptoceratops gracilis Brown 5 



Text Figs. 35, 37 



Holotype- No 5205 A.M.N.H.; parts of skull and jaws, including nasals, maxillaries, portions of the orbital 

 border, back part of crest, dentary, predentary, and splenial; a series of articulated caudal vertebrae; a com- 

 plete fore limb and parts of hind limbs. 



Horizon: Edmonton Cretaceous, about 400 feet above the Pierre. 



Locality: Three miles above Tolman, on the east bank of the Red Deer River, Alberta. 



Collector: American Museum of Natural History expedition of 1910. 



The generic and specific characters are as follows: "Skeleton small. Skull short and deep, 

 without nasal horn. Crest with a high thin sagittal ridge, posterior border of crest smooth; 

 squamosal extending to extreme posterior border of crest. Teeth single-rooted. Dentary massive, 

 short and deep, with less than fifteen rows of teeth; splenial large extending to symphysis. Pre- 

 dentary long and narrow. Manus with digits I, II and III terminating in hoofs; carpals ossified, 

 ulnare and radiale large. Femur straight, with fourth trochanter comparatively large. Tail long 

 and deep, with high slender spines and long chevrons." 



Another fine specimen of Leptoceratops has come to light, collected by Brown, Kaisen, and 

 Tohnson in 1916, from near the bottom of the St. Mary formation, 3 miles west of Buffalo Lake, 

 Montana This specimen, which bears the number 5464 A.M.N.H., is a nearly entire skeleton, 

 except for most of the skull and the fore limbs. The left hind limb is represented by a femur, tibia 



■"' Brown, B., 1914, C. 



