54 SUPPLEMENT ON 



the carpal series, supporting all the rays of the pectoral fin, 

 except the foremost, which is articulated with the radial bone. 

 The posterior extremity varies in position, and is composed of 

 four bones, the largest of which, and also the most constant, 

 being always before the anus and genital orifices, may be 

 viewed as a kind of pubis, and carry upon part of their pos- 

 terior edge the rays of the fin without any intermediate small 

 bones that could be compared to the femur, tibia, peroneum, 

 or tarsal bone. 



The cranium of fishes is in general more distinct and 

 detached from the face, than in other vertebrated animals. In 

 most species the intermaxillary and maxillary bones move 

 upon the cranium by means of diarthroses ; can move inde- 

 pendently of each other, and even independently of the 

 palatino-pterygoi'dian, and tympanal system, which has its 

 own movements. This last-mentioned system, as is also the 

 case with birds and reptiles, forms a plate more or less verti- 

 cal, articulated by its posterior superior angle to the side of 

 the cranium behind the orbit, and anteriorly to the anterior 

 part of the cranium at the side of the vomer ; this anterior 

 extremity partly supports the maxillary bone ; the posterior 

 inferior angle gives the surface for the articulation of the 

 lower jaw. The face has two structures unknown in other 

 classes of animals ; the apparatus of suborbitary bones, form- 

 ing a chain from the anterior frontal to the posterior, and 

 completing below the shrine of the orbit, at a point to which 

 the maxillary and jugal do not extend; and the apparatus of 

 opercular pieces, which adheres to the posterior border of the 

 palatine and pterygoi'dian-tympanal system, protects the 

 branchiae, and opens or shuts according to the movement of 

 the water serving in respiration. Between these four struc- 

 tures, the maxillary, suborbitary, ptery go-tympanic, and oper- 

 cular, is situated the cerebral cavity or cranium, containing as 

 usual, the nose and eye in external cavities, the labyrinth of 



