Miscellaneous. 69 



Dr. Giinther have thought it necessary to separate them. This 

 elimination having been made, the AcantJmri and the four or five 

 allied genera which remain in the family Teuthyes have the closest 

 affinities with the Balistes, as I shall now endeavour to prove. 



In vertebrate animals it is the skeleton that furnishes the most 

 correct indications as to the afiinities and consequently the true 

 characters of the natural groups. The uncertainty in which we 

 still are with regard to the establishment of these groups among 

 fishes will only be dissipated by the determination of their osteo- 

 logical types. The elements of such a work are still too completely 

 wanting to allow of our attacking it as a whole ; but we may prepare 

 the way for it by partial investigations. Thus I now propose to 

 demonstrate the very great analogy and the common characters of 

 the skeletons of the AcantJmri and Balistidse, especially the true 

 Balistes, which are more nearly allied to the Acantlmri than the 

 Triacanthi, MonacantJii, and Aluterce. 



In both groups the jaws arc very small. The border of the upper 

 jaw is formed solely by the intermaxillaries. The maxillaries, which 

 are but very slightly developed, are firmly and immovably attached 

 to the intermaxillaries. This character is the more important be- 

 cause it constitutes, according to Cuvier, the character of the order 

 Plectognathi. Now the AcantJmri deserve to be called Pleetognathi 

 quite as much as the Balistes. The teeth, in both jaws, have the 

 form of incisors. 



The skull is very naiTow. Its upper surface is much elongated 

 and formed by two planes which meet at an obtuse angle above the 

 orbit ; whence it results that the true cranium descends obliquely 

 behind the orbit to meet the vertebral column, instead of being 

 placed in the same horizontal plane as this bony column. It also fol- 

 lows, from this oblique position of the cranial region, that the mas- 

 toid bone is placed very low. It nevertheless presents, in both 

 groups, a large vertical apophysis in front of its articulation with 

 the bones of the shoulder. 



The upper occipital, or interparietal, advances between the prin- 

 cipal frontals, and forms, at the summit of the head, a more or less 

 elevated crest. 



The ethmoid is much elongated ; and consequently the anterior 

 frontals and the palatines are at a great distance from each other, 

 and do not become united to form boiay nasal cavities. 



The anterior sphenoid is produced in front of the orbit in the form 

 of a vertical plate, which meets a vertical plate produced by the 

 ethmoid, and forms with it a bony partition which separates the 

 ethmoid from the palatine arch. 



The vomer is very small, and destitute of teeth. 



The palatines are also small, destitute of teeth, and movably arti- 

 culated with the ethmoid and intermaxillary. 



The different pieces of the temporal wing are not all soldered 

 together, and leave empty spaces merely occupied by the membrane 

 of the palate. 



The opercular flap is formed only by the operculum and the sub- 



