N0.1297. THE OSTEOLOGY OF THE f'APROID FTSHES—STAEKS. 571 



There are four .short actinosts, the upper one the shortest. They 

 are but slightly- constricted at their middles. Three are borne b}' the 

 hypercoracoid; one by the hypocoracoid. 



The first upper short spine or simple ray of the pectoral works 

 directly upon a condyle on the hypercoracoid. 



The postclavicle is a single long spine curving downward toward the 

 ventrals. Its upper end has a thin l)ony lamina developed above and 

 l)elow. It is rirmlv attached to the clavicle above. 



The opposite sides of the pelvic bones are suturally attached to each 

 other. They send a long slender spine forward between the hypo- 

 coracoids and the clavicles. The spine fails to i-each the anterior edge 

 of the clavicles by some distance. A shorter, thicker spine runs for- 

 ward below and at a slight angle with the upper one nearly to the 

 lower end of the hypocoracoid. A thin lamina of bone bridges the 

 space between the spines forming a chamber which is wide open in 

 front and opens behind at each side of a short, vertical, intersecting 

 partition on the lower surface of the girdle just in front of the ventral 

 fins. A short process springs from the upper posterior end, just above 

 the condyle for the ventral fins, and projects a short distance over the 

 fins. 



VERTEBRAL COLUMN AND APPENDAGES. 



There are 9 abdominal vertebra? and 11 caudal, which, w^ith the 

 hypural, make 21. 



The atlas is larger than the other vertebrte and is o])liquely truncated 

 on its lower anterior edge as in Chastodon. 



The zygapophyses are very small and are only developed anteriorly. 



The parapophyses are not developed on the first four vertebrae. 

 They grow progressively longer posteriorly. 



Anteriorly the ribs are borne in pits on the centra of the vertebra. 

 As usual the first two ^'ertebr{e bear only epipleurals. Epipleurals are 

 present on all ri])s and are continued some distance l)ehind the abdoiii- 

 inal cavity. 



The first tiny dorsal spine is attached to a small interneural which is 

 coossified with the second interneural by a thin lamina of bone. The 

 interneural reaches down nearly to the tip of the supraoccipital crest 

 and helps to form the anterior outline of the body. 



The second small dorsal spine is borne by an immense interneural 

 which reaches to the base of the cranium and is clasped ])y two wings 

 from the exoccipitals. A lamina of bone is developed on its posterior 

 edge. 



The third dorsal spine, though many times larger than the second is 

 carried by a smaller interneural. The succeeding interneurals grow 

 progressively smaller. 



