610 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvn. 



VERTEBRAL COLUMN AND APPENDICES OP THE UNPAIRED PINS. 



Abdominal vertebra? 10+caudal l-J:+hypural = 2-i, The atlas is 

 irregularly convex to lit the modified occipital condyle. The sixth 

 vertebra has the first pair of parapophyses developed. The posterior 

 pairs are unconnected by a bridge at their bases. The first two 

 vertebras bear onl}^ single ra3\s in line with the intermusculars, which 

 are developed only on the first few ribs. The neural spines are 

 directed rather irregularly. The interneurals are in greater number 

 than the neural spines below them. Posteriorly the interneurals 

 become directed backward so that they meet the neural spines at an 

 angle, though the latter at this point are somewhat turned forward. 

 The appearance of the interneurals indicate that while holding their 

 connection with the neural spines the dorsal rays have become 

 crowded together. There are four auxiliarj^ interneurals in front of 

 the ray-bearing ones. The first interhsemal is enlarged and expanded 

 in front into a wide, flat plate of bone. The interhsemals exceed the 

 hsemals in number, three or four to one. 



HOLOCENTRUS ASCENSIONIS (Osbeck). 



The top of the cranium is transversely uniformly convex. The occip- 

 ital crest is developed backward, and not at all above the rest of the 

 cranium. The auditory bulla is moderately large, elongate, tube-like, 

 opening to the exterior at its posterior end in a rather large, round 

 hole, w^hich is stopped by a lateral anterior process from the air bladder. 

 The hole is bounded on its inner and lower edges by the basioccipital, 

 on its outer edge by the prootic, and above by the exoccipital. The 

 myodome is large, but is not continued back in a tube. The anterior 

 opening to the cranium is restricted to a very small slit in the middle 

 of the anchylosed orbitosphenoids, and a slightly larger hole, inclosed 

 at its sides and posterior end by the basisphenoid, at its anterior end 

 by the united alisphenoids. 



The supraoccipital shows very little of its upper surface, being cov- 

 ered by the frontals, but projecting slightl}' between their posterior 

 ends. Its crest is confined entirely to its posterior vertical surface. 

 The basioccipital and exoccipitals form the occipital condyle as usual, 

 though the notch between them is deeper than in the other families. 

 The pit in the basioccipital is near its upper edge. Just anterior to 

 the condyle, and between the openings to the auditory bulla?, the 

 basioccipital is compressed. The frontals are exceedingly large, pro- 

 jecting posteriorly almost to the posterior angle of the cranium, where 

 the cranium drops ofl' at a right angle, and becomes vertical. They 

 cover almost the entire parietals, which in turn cover the upper sur- 

 face of the epiotics, the supraoccipital, as described, and much of the 



