4 ARKIV FÖR ZOOLOGI BAND S. N:0 18. 



Infracarinal muscles are developed behind the anal fin. 

 The pelvic fins are, as is well known, reduced. The skeleton 

 of these fins consists in Balistes of a median unpaired bone 

 which has been called the »pelvic bone» by the authors. 

 This bone carries a spine which is movable. The spine can 

 be erected by a muscle which lies in a median ventral groove 

 of the pelvic bone (Fig. 16). The muscle continues into a 

 rather long tendon which is inserted into the spine. This 

 muscle is probably formed by the coalescence of the origi- 

 ginally paired muscles of the pelvic fins. The pelvic bone 

 itself can be moved a little in Balistes by a paired muscle 

 which takes its origin from the lateral triangulär depression 

 of the anterior part of the pelvic bone. The muscles are 

 inserted into the pectoral archs (Fig. 15). These muscles 

 correspond, without doubt, to a portion of m. rectus of Mau- 

 rer's diagram or m. infracarinales of other authors. 



The muscles of the first dorsal fin have been described 

 by Meckel and Sörensen. There are no inclinator-muscles. 

 The fin contains three spines, the depressor- and erector- 

 muscles of which have been figured and described by Sö- 

 rensen for both Balistes and Monacanthus. As my studies 

 on Balistes have given the same results, I refer to his paper. 

 The second dorsal fin is provided with superficial inclinator- 

 muscles. Meckel has shown that the profound muscles of 

 this fin, m. erectores and m. depressores, act mainly as incli- 

 natormuscles. The two muscles for each fin-ray are, how- 

 ever, contrary to Meckel's view distinct and have distinct 

 tendons, but the structure of the joint between the fin and 

 the pterygiophores makes the fin somewhat movable from 

 side to side, but very little, if at all, in a cranio-caudal direc- 

 tion. That is to say, the fin cannot be depressed. The 

 action of the muscles results in an inclination of the fin from 

 side to side. 



The muscles of the anal fin are quite similar to those 

 of the second dorsal fin except that the first superficial 

 inclinatormuscle is very large. 



