FISHES OF HAWAIIAN ISLANDS. 
441 
Suborder OSTRACODERMI. — The Trunk Fishes. 
This group includes those Plectognaths which are without spinous dorsal and which have the body 
inclosed in a 3-angled, 4-angled, or 5-angled box or carapace, formed by polygonal, bony scutes, firmly 
joined at their edges, and with distinct teeth in the jaws. There is but one family, the Ostraciidse, a 
singular offshoot from the Sclerodermi. 
Family LXXXII. OSTRACIM.— The Trunk Fishes. 
Body short, cuboid, triquetrous or pentagonal, covered by a carapace formed of firmly united 
polygonal bony patches, the jaws, bases of the fins, and caudal peduncle free and covered by smooth 
skin. Mouth small; each jaw with a single series of long, narrow teeth ; maxillaries and premaxil- 
laries firmly united; gill-opening a nearly vertical slit, below and behind the eye; dorsal fin single, 
short, without spine; anal short, similar to dorsal; caudal rounded; no ventral fins; vertebrfe 14, the 
anterior 9 elongate, the last 5 extremely short; no ribs. Genera 3; species about 20, all of the tropical 
seas, living near the bottom in shallow waters. The species of this group are so singular in appearance 
and so easily preserved that they have been common in collections ever since the collecting of tropical 
curiosities began. The 4 American species were well known to Artedi and Linnaeus. “ The locomo- 
tion of the trunk fishes is very peculiar. The propelling force is exerted by the dorsal and anal fins, 
which have a half rotary, sculling motion, resembling that of a screw propeller; the caudal fin acts as 
a rudder, save when it is needed for unusually rapid swimming, when it is used as in other fishes; the 
chief function of the broad pectorals seems to be that of forming a current of water through the gills, 
thus aiding respiration, which would otherwise be difficult on account of the narrowness and inflexi- 
bility of the branchial apertures. When taken from the water, one of these fishes will live for 2 or 3 
hours, all the time solemnly fanning its gills, and when restored to its native element seems none the 
worse for its experience, except that, on account of the air absorbed, it can not at once sink to the 
bottom.” (Goode.) 
a. Carapace 4-angled. 
b. Carapace entirely without spines Ostracion, p. 441 
bb. Carapace with 2 preocular spines and 2 terminating the ventral keels Lactoria, p. 444 
aa. Carapace 6-angled Aracana, p. 446 
Genus 200. OSTRACION Linnaeus. 
Trunk-fishes with the carapace closed behind the anal fin; carapace with or without frontal and 
abdominal spines; dorsal rays 9 or 10; candal rays always 10; lateral ridges developed; median dorsal 
ridge undeveloped, or else raised in a sharp spine, the body therefore 4-angled or 5-angled. Although 
this character is a striking one it is not one of high structural importance. Hollard and Bleeker have 
discarded it as being of no real systematic value. All writers agree that the species of the group are 
most closely related, and that the relations are closer than they appear. We think, with Doctor 
Goode, and Jordan and Fowler, that the shape of the carapace affords the most reliable guide to the 
arrangement of the species of the genus, and we find it difficult to define more than 2 genera in the 
family, unless we assign generic rank to each of the leading sections. In Japan 3 of these sections are 
represented, Tetrosomus, Lactoria, and Ostracion. The remaining 4, Rkinesomus , Chapinus, Lactopkrys, 
and Acanthostracion are all based on 3-angled species, a type confined to the West Indian region and 
taken as a distinct genus, Lactophrys, by us in our Fishes of North and Middle America. 
Ostracion Linnaeus, Syst. Nat., 10th ed., 330, 1768 (many species; first restricted by Swainson to 4-angled forms, cubicus 
taken as type). 
Tetrosomus Swainson, Classn. Fish., ii, 323, 1839 ( turritus ). 
Cibotion Kaup, Wiegmann’s Archiv Natur. 1855, 215 (cubicus). 
a. Ventral surface of carapace without spots; anterior opening of carapace broad, greater than orbit. 
b. Sides of body with golden spots sebie, p. 442 
bb. Sides of body entirely without spots oahuensis , p. 443 
aa. Ventral surface of carapace with small bluish white spots or reticulations; anterior opening of carapace narrow, its 
width less than orbit lentiginosum. p. 443 
