in the Fish Gallery of the Indian Museum. 77 



usual form, but the gill-openings are narrow slits. The 

 skeleton is incompletely ossified and the vertebrae are 

 few in number. There is no pneumatic duct to the air- 

 bladder. The suborder consists of two families. 



Family I. Sclerodermi [Cases 74-75]. 



In this family there are distinct teeth in the jaws, 

 there is generally a spinous dorsal fin, and the ventral 

 fins are generally represented by a pair of spines. It is 

 divided into three subfamily groups : — 



1. Subfamily Triacanthina, of which three Indian 

 genera are known, namely Triacanthus, which is a shore 

 fish, and TriacantJwdes and Haiimochirurgus which 

 belong to the deep-sea. Haiimochirurgus has the snout 

 produced to form a long tubular beak. In all the mem- 

 bers of this subfamily the skin is covered with small 

 prickly scales, there is a spinous dorsal fin, and a pair of 

 very strong ventral spines which can be erected and 

 fixed like bayonets. 



2. Subfamily Balistimz, of which three genera are 

 known, all being represented in Indian Seas. They are 

 Batistes, known as File-fishes, or Trigger- fishes, the 

 species of which are very numerous round coral-reefs ; 

 Monacanthus of which the species are abundant among 

 coral-reefs but often also take to the open sea, swimm- 

 ing chiefly by rapid vibrations of the soft dorsal fin ; 

 and Anacanthus, which resembles Monacanthus in form 

 and habit, but has a barbel at the chin. The members 

 of this subfamily have strong chisel-like teeth with 

 which they bite off the pieces of coral and chip open the 

 mollusks upon which they feed : their skin is covered 

 either with granules or with hard rough bony scales, 

 and the ventral spines are rudimentary or absent. Both 

 Batistes and Monacanthus are also found in the tropical 



