Cope.] I'JO [May 15, 



The supraoccipitals have considerable extent on the superior face of the 

 skull. The largest bones are the parietals, whose median suture is 

 interrupted by the foramen at about the middle. The next largest 

 bone is the tabular, which extends half the length of the parietal for- 

 wards. The supramastoid is pyriform and is rather small, and its anterior 

 angle is wedged in between the posterior parts of the postfrontal and post- 

 orbital. The postfrontals separate the frontals from the orbital border. 

 The frontals are distinct, and their posterior border is about in the line 

 of the posterior borders of the orbits. The supratemporal region is in- 

 jured, and only the suture between the quadratojugal and jugal is visible. 

 The sculpture consists of radiating ridges from some point in each 

 bone to its circumference. This point may be near the centre or one of 

 the borders of the bone. The ridges maj' be more or less interrupted 

 and inosculating. They are present on the lower jaw as well as the 

 upper. 



Measurements. mm. 



Length of skull on base including symphj'sis 40 



Width of skull at quadrate articulations 36 



Length of mandibular angle from do 6 



Transverse diameter of orbit 5 



Length from posterior border of skull to orbit. ........ 18 



Width between nostrils 10 



From the Permian bed of Texas. 



EXPLANATION OF PLATES. 



Pl.\te YII. 



Otocmlus testudi/ieus Cope ; parts of skull and skeleton with carapace, 

 from above ; two-thirds natural size. 



Plate YIII. 



Otocoelus testmUneus Cope ; specimen figured on preceding plate, from 

 below ; two-thirds natural size. 



Plate IX. 



Fig. 1. Otocoelus mimeticus Cope ; skull and part of carapace in con- 

 tinuous relation in the matrix, from above ; three-tifths nat- 

 ural size. 



Fig. 2. Otocoelus testudineus Cope ; broken edge of typical specimen 

 representing sections of ribs and carapacial bands near the 

 vertebral column : two-thirds natural size. 



