GEOWTH. 



173 



and hide tlie dorsal and ventral fins. The plates attached to 

 the shoulder-girdle remain persistent until the young fish 



Fig. 87. — Tholiclitliys-stage of Pomacantlms (magn.) Atlantic. 



has assumed the form of the adult; thus thej are still 

 visible in young Chcetodon citrinellus, 

 30 millimetres long, in which the 

 specific characters are already fully 

 developed.^ — The Sword-fishes with 

 ventral fins {Eistiophorus) belong 

 to the Teleosteans of the largest size ; 

 in young individuals, 9 millimetres 

 long (Fig. 89), both jaws are pro- 

 duced, and armed with pointed teeth; the supra-orbital 

 margin is ciliated; the parietal and praeoperculum are pro- 

 longed into long spines; the dorsal and anal fins are a 

 low fringe, and the ventrals make their appearance as a 

 pair of short buds. "When 14 millimetres long (Pig. 90) 

 the young fish has stiU the same armature of the head, 

 but the dorsal fin has become much higher, and the ventral 



Fig. 88.— Young ChaBtodon 

 citrinellus (30 mill. long). 



