PLATE IX. 



Enchodus petrosns Cope. 

 The pair of palatines represented on this plate is the same as that 

 shown on plate VIII, viz., specimen No. 198 of the American Museum. 

 In this cephalic view the layer of new bone tissue on the end of the left 

 palatine is shown a little more distinctly than in plate VIII. In the 

 process of removing the gypsum crystals from this portion of the bone, 

 the lateral margins of the layer were broken off before the nature of it 

 was discovered. The upper opercular (op) belongs to the same specimen. 

 The lower of the opercular bones (op) belongs to specimen No. 804 in 

 the University of Kansas Museum. The upper portion of this opercular 

 is absent, but the similarity of the tuberculation and ridges on the 

 outer surface of these two operculars is so striking that there seems 

 little doubt that they belong to the same species. While on the opercular 

 of the American Museum specimen there is only a small ai'ea just 

 caudad to the point of suspension to the hyomandibular, which shows 

 the tubercles distinctly, this is to be accounted for by the fact that most 

 of the surface of this opercular was injured by the crystallized gypsum 

 with which the bones of this specimen were originally enveloped. The 

 larger ridges extend mostly dorsally and ventrally, gradually becoming 

 smaller and more tuberculated caudally, the intermediate area being 

 much tuberculated, but free from ridges except near the point of suo- 

 pension, where they are very short and small, nit, metapterygoid ; vt, 

 vertebra. 



