FAA: TELEOSTEI CHAP. 
rough spine at the end of the long, movable pelvis. Body covered 
with juxtaposed movable scutes or with minute rough scales. 
About 100 species are known from the tropical and warm 
seas, one species (Balistes capriscus) occasionally wandering as far 
north as the south coast of England. Genera: Lalistes,. Mona- 
canthus, Paraluteres, Pseudaluteres, Pseudomonacanthus, Aluteres, 
Psilocephalus. The Oligocene genus Acanthoderma is closely 
allied to Balistes. 
The “ File-Fishes ” or “ Trigger-Fishes ” (Lalistes), the largest 
species of which grow to nearly 3 feet, have a powerful dentition, 
which enables them to break off pieces of corals, on which they 
feed, and to bore holes in the hard shells of Mollusca in order to 
extract the soft parts; they are themselves well protected by a 
mail of hard, rhomboidal scales. The herbivorous J/onacanthus 
is less favoured in this respect, the rough scales being so small as 
to give the skin a velvety appearance. 
Psilocephalus differs from Monacanthus in its very elongate 
head and body, the very feeble dorsal spine, the presence of a 
mental barbel, and its more numerous vertebrae (29 or 30 instead 
of 18 to 21). The flesh of many of these fishes is poisonous.’ 
The drumming sounds produced by Balistes have been described 
by Mobius. 
Fam. 4. Ostraciontidae.—Praemaxillaries not protractile, 
firmly united to the praemaxillaries ; teeth incisor-like ; palatine 
immovable. Gills 4.. Praecaudal vertebrae with very feeble para- 
pophyses and no epipleurals. No spinous dorsal fin. Clavicles, 
coracoids, and post-clavicles much expanded. No ventral fins. 
Body encased in a carapace formed of large, juxtaposed, mostly 
hexagonal bony plates. Vertebrae 14 to 16. 
The species of “ Trunk-Fishes ” number about 20, and are refer- 
able to 3 genera: Aracana, Ostracion, Lactophrys ; all belong to 
the tropical seas, hving near the bottom in shallow water. The 
genus Ostracion is represented by one species in the Upper 
Eocene. 
The rigid box in which these fishes are encased entails more 
use of the dorsal and anal fins for progression than is customary 
1 Cf. Pellegrin, Poissons Vénénewx (Paris, 1900, 8vo), which contains a 
very full résumé of what is known of the toxic properties of the various 
Plectognaths. 
* Sitzb, Akad. Berl. 1889, p. 999. 
