78 NEW REPTILES AND STEGOCEPHALIANS FROM 



DESCRIPTION OF THE REMAINS OF DINOSAURS. 



Certain specimens collected in Crosby County, in the same beds with the 

 Phytosaurs, indicate the presence of a small Dinosaur. Notable among these are 

 a posterior cranial region (No. 7473, University of Michigan) and a string of cer- 

 vical and anterior dorsal vertebrae (No. 7507). Both of these specimens were 

 collected on the west side of the Blanco River, north of Cedar Mountain, the first 

 in the breaks to the south of the old Spur-Crosbyton mail-road and the second in 

 the breaks just north of that road. 



The cranial region is well preserved in a hard matrix of clay, which has permitted 

 the working out of the smaller details and the foramina of the region. As shown in 

 plate 13 D to F, the basicranial floor is preserved as far forward as the hypophysis. 

 The distal portions of the exoccipital opisthotics are lost. The occipital condyle is nearly 

 hemispherical, with an extremely short neck. The portion of the basioccipital below 

 the condyle descends almost vertically and the posterior edges of the tubera are' not in 

 advance of the anterior edge of the condyle. The vertical portion of the basioccipital 

 is deeply concave posteriorly and the lower face of the neck of the condyle is perforated 

 by two small foramina near the middle line, probably for nutrient vessels. The sutures 

 between the basioccipitals, exoccipitals, and supraoccipitals can not be made out. 

 The foramen magnum is depressed oval in outline, with the transverse axis nearly as 

 great as the width of the condyle. The supraoccipital is smooth, slightly concave, and 

 slants upward and forward to the rough, incomplete edge, which must have been very 

 near to the articular surface for the bones above. As described by Huene in Anchisaurus, 

 the exoccipital has three ridges; one runs inward and backward to the upper outer 

 edge of the condyle, one downward on the outer side to the tubera, and one outward 

 and backward to form the lower edge of the opisthotics. In the angle formed by the 

 last two there is the good-sized opening of the foramen for the XII nerve. This foramen 

 can be traced on the broken surface of the bone to its opening on the inner side, not 

 far within the edge of the foramen magnum. 



The lateral view of the specimen (plate 13 E) displays the peculiar characters 

 of the skull most strikingly. The inner portion of the opisthotic and the prootic meet 

 in a smooth concave surface which is inclined to the posterior surface of the supraoccipital, 

 so that the two would meet at a sharp angle. The beginning of the opisthotic shows that 

 that bone extended outward and backward and slightly upward. On its lower side is 

 a deep groove which leads into the surprisingly large otic cavity. Below this cavity the 

 basisphenoid extends downward, terminating in the long and slender basipterygoid 

 processes. The distal ends of these processes are broken away, so that it is impossible to 

 determine the nature of the articulation with the pterygoids. The basipterygoid pro- 

 cesses are rounded and heavier behind, but become very thin anteriorly; the anterior 

 edges are broken away, but it appears that the processes of the two sides came together, 

 or very nearly so, in the median line. Between and beneath the anterior portions of the 

 process is a large cavity extending forward as far as the groove on the side of the basi- 

 sphenoid described below. This cavity is apparently blind; no openings in its wall have 

 been detected, though an artificial opening was made by the needle in the thin anterior 

 portion. The side of the basisphenoid is peculiar. In the broken condition of the speci- 

 men it appeared as if the bone were composed of two parts, an anterior overlapping below 

 on to the posterior part, which in turn overlapped in the same way upon the basioccipital; 

 this appearance, however, is less apparent when the upper half of the brain-case is 

 put in place, for the upper part of the apparent groove on the side of the basisphenoid 

 is resolved into a part of a foramen. The anterior portion of the basisphenoid has 



