NEMATOGNATHI. 65 



Rhineastes calvus Cope. 



Annnal Report U. S. Geol. Surv. Terrs., 1872 (1873), p. 640. 

 Plate V, figs. 3-4. 



Represented by several specimens, including most parts of the cranium, 

 spines, etc. 



One of these shows the supraoccipital production to have the form of 

 an equilateral triangle, with a sinus of the posterior border on each side of 

 it, which advances in front of the epiotic bone below. Shortly in front of 

 this point the deep groove representing the fontanelle commences. The 

 cranial rugae are lines parallel to the fontanelle, which diverge to the 

 margins of the occipital prolongation, and are frequently connected by 

 cross-ridges. The frontal portion of the skull is much expanded laterally, 

 and the part beneath inclosed by the prefrontals, particularly wide. The 

 fontanelle in this region does not appear to have been entirely closed. 

 The surface is here also strongly rugose. The vomer has a T-shaped 

 anterior extremity, which is immediately followed by two transverse paral- 

 lelogrammic patches of premaxillary brush-teeth in several rows. They 

 are about twice as long as wide, and in contact medially. The anterior 

 margin of the premaxilla projects their length beyond them, and is perfectly 

 smooth, and has a smooth, rounded border. The basioccipital has a sub- 

 cordate cotylus. In front of the median inferior pit are three groove-pits ; 

 the articular face for the post-temporal is opposite the former and is rugose 

 and has strongly reverted edges. 



Measurementg. 



M. 



Diameter occipital articulation DOBS' 



Diameter base supraoccipital shield 0130 



Width front above orbits 0043 



Length from vomer to premaxillary border 0110 



Length of both tooth patches 0120 



Diameter pectoral spine at base 0031 



The pectoral spine is seiTate on both edges. The base of the dorsal is 

 symmetrical and articulates with its intemeural bone by two lateral flat, 

 and one convex median anterior surfaces, whose surfaces are curiously 

 rugose. The intemeural has a rugose median superior keel, which termi- 

 nates in a point which is received into a pit of the base of the spine ; there 

 5 o 



