No. I.] THE GENUS OF FOSSIL FISHES. 53 



speaks of the two maxillary condyles of that species as being 

 large and separated by a space. This description, though 

 vague, would fit my specimen. But X. lestrio is stated to have 

 three, and sometimes four, premaxillary teeth. As I have 

 said, I find no evidence of a third tooth. The total length 

 of the upper jaw of my specimen, including the premaxillary, 

 is 380 mm. The height of the maxillary from lower border 

 to top of posterior condyle is 125 mm., almost exactly one- 

 third the length. Applying this proportion to Cope's figure 

 of X. lestrio {Cret. Vert., PL XLII, Fig. i), we find that 

 his drawing of the maxillary would have to end at the right 

 hand within about 8 mm. beyond its present limit, in order to 

 represent the complete bone. It is very evident that a much 

 more considerable piece of that maxillary was wanting. Had 

 this missing portion of that bone had the form and proportions 

 possessed by my specimen, the drawing would have to extend 

 25 mm. further to the right. This would make the jaw much 

 longer in proportion to its height than my specimen. 



As a matter of fact, I find no serious discrepancy between 

 Cope's description of his PortJieiis tJiauinas and my specimen. 

 I give description of the upper jaw. 



Upper jaw heavy and massive ; its height being apparently 

 greater in proportion to its length than in other species, one to 

 three. Premaxillary broadly oval ; its major axis 130 mm., its 

 transverse 1 10 mm., its greatest thickness 40 mm. Teeth 

 two, the most anterior projecting 55 mm. beyond the bone ; 

 its diameter at base 20 mm. Second tooth 22 mm. long, prob- 

 ably not full grown. Maxillary extending forward against inner 

 surface of premaxillary nearly to the anterior border of latter. 

 Condyles as shown in Fig. 2. Tooth border sinuous, slightly 

 concave just behind premaxillary suture, then convex to beyond 

 large teeth, then again more strongly concave ; finally convex, 

 and rounding into the distal border. Upper border descending 

 rapidly from posterior condyle and concave to point three-fifths 

 of distance to distal extremity, there forming an angle, and 

 again concave until it begins to round into the distal border. 

 In general, the distal third of the maxillary bends downward 

 instead of upward. On dental border there are in front, first. 



