FISHES. 317 



support the fin before, or, in other words, they place it in an angle 

 with the body which is more or less wide, the two posterior layers 

 bring it nearer and stick it against the body. Each layer, by its 

 independent action, may raise or depress the fin according to its 

 direction. Sometimes a process is detached from the deep posterior 

 layer which, carrying its tendon over the superior border, becomes a 

 special elevator of the fin : it is by the combination of these various 

 actions that the pectoral extends or contracts. In those species in 

 which the carpus is prolonged, as in the lophius, these special muscles 

 are much more developed. 



These are the layers of which we at first spoke, and which being 

 enlarged gradually in the squalus, become at last the enormous 

 muscles of the wings of the ray, that form the greatest proportion of 

 the edible flesh of this fish. 



The Muscles of the Pelvis. 



The bones which support the ventral fins, and to which we have 

 applied the name of bones of the pelvis, are put in motion forward 

 and backward by the lower thin muscles of the trunk (No. 6) already 

 spoken of. The anteriors proceed from the internal extremity of 

 the humeral bones, and are inserted into the inferior surface of the 

 bones in question near their internal border. The posteriors are 

 connected to the posterior border of the bone of the pelvis, and 

 directing themselves towards the anus surround that aperture, and 

 are either lost amongst the lateral muscles, or become attached to the 

 first interspinals of the anal fin. The anteriors are sometimes 

 subdivided. In that species which have the ventrals attached beneath 

 the throat or thorax, they are very short, and are very intimately 

 united with the great lateral muscles. 



These bones of the pelvis are moved towards one another by trans- 

 verse muscles, placed beneath their inferior surface, of which one 

 part is occasionally crossed ; but they do not invariably exist. The 

 perch, for instance, has none ; and it is probable that they are not to be 

 found in any of the species, where the bones of the pelvis are united 

 by a suture. On the other hand, we find them very large in the 

 lophius, where these bones are separated from each other. 



The pelvic bones receive from the large lateral muscles, between 

 which they are situated, a slip which draws them from the side ; but, 

 generally speaking, their motions, as well as those of the two bones 

 of the shoulder, are very much limited. 



Muscles of the Ventral Fins. 



They are supported by the bones of the pelvis ; the depressors on 

 their lower surface (Nos. 17, and 18); the elevators on their upper. 

 Two layers on each surface, crossing one another a little like those 

 of the pectorals, separate into as many slips as there are rays, and 

 are more or less distinct, as those rays are more or less separated and 

 have the power of motion more independent. The more external of 

 the slips (No. 17), are more generally separated, and serve to dilate 

 the fins. 



These proper muscles of the rays of the extremities, both of the 



