length of the pelvis. Anteriorly the pelvis articulates by 

 tough fibrous tissue with the medial edges of the two 

 cleithra in the region below the quadrate. There is no 

 trace of pelvic fins or of any of the rudimentary fin ray 

 elements such as are found in balistoids. 



VERTEBRAL COLUMN. —All vertebrae with bicon- 

 cave centra, except for the last, which ends posteriorly in 

 the urostyle. 



Abdominal Vertebae. 



First vertebra. — Lateral wall of neural arch from 

 each side of the centrum meeting its opposite member 

 dorsally above the neural canal but not continuous or in- 

 terdigitated with it; rather, the medial edges are held to 

 one another by fibrous tissue; the dorsal surface of this 

 articular area is slightly upraised medially to give the 

 suggestion of a neural spine. The upper anterior portion 

 of the centrum and lower portion of the neural arch are 

 deeply concave and form a facet for articulation by fi- 

 brous tissue with the exoccipital condyle. 



Other abdominal vertebrae. — Nine abdominal 

 vertebrae in two specimens, all of which, except for the 

 first and ninth in the smaller specimen, bear true ribs; 

 from the first to the ninth vertebrae the neural spines 

 become increasingly well developed; the two halves of 

 the neural spine of the second vertebra, like that of the 

 first, are not fused together above the neural canal, but 

 are held to one another by fibrous tissue, while the neural 

 spines of the more posterior vertebrae are single pieces. 

 The first to the sixth abdominal vertebrae do not possess 

 haemal arches, but the seventh to ninth have complete 

 haemal arches and progressively better developed 

 haemal spines which project slightly posterior to the 

 haemal arch, that of the seventh with only a short pos- 

 terior tapering to the haemal arch. Haemal prezyga- 

 pophyses are not developed and haemal postzyga- 

 pophyses only begin to develop from about the seventh 

 vertebra and never extend posteriorly even to the level of 

 the end of the centrum above them. Neural postzyga- 

 pophyses are present on the abdominal vertebrae, but 

 the greatest development of the zygapophyses involves 

 the neural prezygapophyses. The neural pre- 

 zygapophyses, and particularly the portions of the neural 

 arches and spines above them, become enlarged from the 

 second to about the seventh and eighth abdominal verte- 

 brae. At its full development the region anterior to the 

 thickened shaftlike part of the neural spine becomes en- 

 larged into a relatively flat plate which projects ante- 

 riorly slightly past the anterior edge of its vertebral cen- 

 trum to fit below the posteriorly projecting neural spine 

 of the preceding vertebra. These anterior expansions are 

 held by fibrous tissue to the posterior edge of the neural 

 spine region of the preceding vertebra and increase the 

 rigidity of the vertebral column. The tip of the neural 

 spine of the fourth vertebra supports the anteroventral 

 edge of the first supraneural ( = first basal pterygiophore 



of the spiny dorsal fin when the latter is present), while 

 the neural spines of the fifth and sixth abdominal verte- 

 brae articulate with the ventral edge of this element fur- 

 ther back along the length of the latter. The neural spine 

 of the seventh abdominal vertebra articulates dorsally 

 with the ventral edges of the second and third supra- 

 neurals (terminology when no spiny dorsal fin is present) 

 and posteriorly with the anterior edge of the first soft dor- 

 sal fin basal pterygiophore. The neural spines of the 

 eighth and ninth abdominal vertebrae articulate be- 

 tween the more anterior dorsal fin basal pterygiophores. 



Ribs and epipleurals. — True ribs are present on all 

 of the abdominal vertebrae in the large specimen, but are 

 absent on the first and last abdominal vertebrae in the 

 smaller (illustrated) specimen. The point of articulation 

 of the rib with the vertebra is at first with the lower 

 anterolateral surface of the centrum, but it becomes 

 progressively lower on the centrum until finally the ribs 

 on the last few abdominal vertebrae articulate with the 

 lateral surfaces of the haemal arches. The ribs become 

 progressively longer from the first to the fourth or fifth, 

 and then become slightly shorter again. The ribs border 

 the internal surface of the abdominal cavity and there 

 can be no doubt that they are pleural ribs. The first two 

 ribs (attached to the first and second vertebrae) of the 

 larger specimen and the first rib (attached to the second 

 vertebra) of the smaller specimen do not bear epi- 

 pleurals (intermuscular bones), but all of the other ribs 

 have well-developed epipleurals attached to their dorsal 

 surfaces. In the smaller of the two study specimens the 

 epipleurals attached to the second to fifth abdominal 

 vertebrae are composed of two pieces which are variously 

 branched. The two pieces of these intermuscular bones 

 are held together by fibrous tissue. The epipleurals at- 

 tached to the sixth and seventh ribs are composed of a 

 single unbranched piece, and while that of the sixth 

 vertebra is held by fibrous tissue to the pleural rib, that 

 of the seventh vertebra is fused to the rib. The ninth ab- 

 dominal vertebra has an unbranched epipleural attached 

 by fibrous tissue to the lateral surface of its haemal arch. 

 Short, unbranched epipleurals are attached by fibrous 

 tissue to the lateral surft e of the haemal arches of the 

 first five caudal vertebrae. In the larger study specimen 

 the epipleurals are more extensively branched, and only 

 one, that attached to the fifth abdominal vertebra, is 

 composed of two pieces. The epipleurals of the second 

 abdominal vertebra are both unbranched, while those of 

 the third are branched on one side and unbranched on 

 the other. The epipleurals of the fourth to seventh ab- 

 dominal vertebrae are extensively branched, while those 

 on the eighth and more posterior vertebrae are un- 

 branched. Whereas in the smaller specimen the 

 epipleurals extend to the fifth caudal vertebra, in the 

 larger there are epipleurals on both sides of the sixth 

 caudal vertebra as well. 



Caudal Vertebrae. — Eleven caudal vertebrae in two 

 specimens; all, except the last, with well-developed 

 haemal arches and spines; neural spines well developed 



