328 ACRONTTRID.E, 



panic especially is well developed, occupj-ing the whole of the ante- 

 rior side of the proeoperciilum. The prajorbital is very elongate ; the 

 other hones of the infraorbital ring are fii-mly united together, and 

 the posterior ones are in immediate contact with the inner ridge of 

 the praeoperculum, as in Chatodon. The angle formed by the limbs 

 of the praeoperculum is veiy obtuse ; the lower limb has only half 

 the length of the posterior : operculum rather narrow and elevated, 

 not extending downwards to the angle of the praeoperculum, where 

 ifris replaced by the suboperculum : interoperculum small. 



The bones of the humeral arch are rather strong : the siiprascapula 

 is fii-mly imited with the skull ; scapula long, broader in its inferior 

 half than in its superior; coracoid very long and strong, straight. 

 The cavity for the pectoral muscles, which is formed by the humerus 

 and the bones of the fore-arm, is very broad and rather deep ; its 

 bottom is nearly entii'ely osseoiis, the ulna having a small foramen, 

 the radius a larger and a smaller one. The pubic bones are very 

 long, slightly bent, and firmly attached to each other, leaving scarcely 

 any free space between them. 



There are nine abdominal and thirteen caudal vertebrce, the length 

 of the former portion of the vertebral column being to that of the 

 caudal as 1 : 1'66. The vertebrae are somewhat elongate, not com- 

 pressed. All the apophyses are strong, and those of the anterior 

 caudal vertebraj rather long. The nem-als and interneurals of the 

 abdominal vertebrae are so dilated into lamellae posteriorly, that the 

 whole forms one continuous osseous plane, without free spaces be- 

 tween the single bones. The first interneural is exceedingly strong 

 and compressed ; it is dilated superiorly, the dilated portion ending 

 in a spine anteriorly, behind which is a deep incisure to receive the 

 base of the fii'st dorsal spine. The second interneural is finnly 

 attached to the fii'st. The interneurals of the following dorsal spines 

 are dilated superiorly into a slightly concave plate, as in Teuthis, and 

 one always corresponds to a single neural, whilst each neural and 

 haemal of the caudal vertebrae always support two interneurals and 

 interhaemals of the soft rays. The first interhaemal is similar in 

 structure to the first interneiu'al, but much longer, and its dilated 

 portion has no spine anteriorly. Eibs well developed, with epi- 

 pleurals. 



lines. 



Length of the first vertebra Ol- 



of the second vertebra l| 



of the third vertebra 11 



of the fourth vertebra 2-L 



of the tenth vertebra 2| 



of the- twentieth vertebra 2 



of the abdominal portion 19 



of the caudal portion 31| 



of the eleventh neui'al spine 11 



of the first haemal spine 14 



— of the first internem-al spine 7 



of the fu'st interhaemal spine 19 



