346 
BULLETIN OF THE BUREAU OF FISHERIES 
194. Lactophrys trigonus (Linnaeus). Trunkfish; Shellfish; Boxfish. 
Ostracion trigonus Linnfeus, Syst. Nat., ed. X, 1758, p. 330; “India.” 
Lactophrys trigonus Uhler and Lugger, ed. I, p. 88; ed. II, p. 74; Jordan and Evermann, 1898, p. 1723, PI. CCLXIII, fig. 641 . 
A single very small individual, described as follows, is at hand. In this species the young 
differ greatly from the adult. 
Head 2; depth 1.3; D. 9; A. 9. Body more or less four-angled, with a prominent median 
ridge on back; the carapace open behind dorsal and without spines; head very deep; snout not 
much in advance of forehead, 3.2 in head; eye 4; interorbital 2.3; mouth very small, terminal; 
dorsal and anal fins similar; caudal fin round; pectoral fins broad, the upper rays longest, 3.5 in 
head. 
Color in alcohol uniform brownish; fins plain translucent. 
A single small specimen 20 millimeters in length was secured. This is the only trunkfish 
known from Chesapeake Bay, and it is readily recognized by the hard, boxlike shell that covers 
the body. 
The young are very different from the adult. In large individuals the body is sharply three- 
angled, and the ventral ridge of the shell, somewhat in advance of the vent, bears a large, flat spine. 
This spine is undeveloped until the fish reaches a length of about 35 millimeters. The body in the 
adult is more elongate and not as deep, the depth being contained in the length from 2.6 to 2.8 
times. The head in the adult is contained 3.8 times in the body. 
This fish reaches a maximum length of about 1 foot. Its flesh is of excellent flavor, and at 
Key West, Fla., and Colon, Panama, at least, it is used as food. 
Habitat . — Woods Hole, Mass., south to Bahia, Brazil; apparently uncommon north of Florida. 
Only the young appear to have been taken north of Florida. 
Chesapeake localities. — (a) Previous records: “Occurring very rarely in the salt waters of the 
southern part of Chesapeake Bay and around the extremity of St. Marys County” (Uhler and 
Lugger, 1876). (b) Specimen in collection: Cape Charles, Va.; evidently very rare in Chesapeake 
Bay. 
Family XC. — TETRAODONTIEMi. The swellfishes 
Body oblong or elongate, usually about as broad as deep; belly usually capable of great infla- 
tion with water or air, or both; mouth small, terminal; teeth in the jaws fused, forming a continu- 
ous cutting edge, except for a median suture; gill slits small, situated in front of pectorals; scales 
present or absent; the skin often bearing prickles; lateral line conspicuous or not; dorsal fin inserted 
posteriorly, composed of soft rays only; caudal fin various in shape; anal fin similar to the dorsal 
and usually opposite it; ventral fins wanting; pectoral fins short and broad. 
The members of this family mostly inhabit warm shore waters. They are sluggish swimmers 
but find a measure of protection in their tough and often prickly skin and by greatly increasing 
their size, through inflation, which also causes the prickles to stand erect and to appear much more 
prominent than before inflation. Some of the members of the family attain a considerable size, 
but none are of commercial importance, as their flesh is said to be rank and sometimes poisonous. 
Two genera and three species are known from Chesapeake Bay. 
KEY TO THE GENERA 
a. Body comparatively elongate; dorsal and anal fins rather long, each with 12 to 15 rays; skin 
largely smooth Lagocephalus, p. 347 
aa. Body oblong, plump; dorsal and anal fins smaller, each with six to eight rays; skin largely 
prickly Tetraodon, p. 347 
