278 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxv. 



Suborder OSTRACODERMI.' 



This group iiu-lndes those Plectognaths which are without spinous 

 dorsal and which have the body inclosed in a S-ang-led, l-angled, or 5- 

 angled box or carapace, formed l)y pol3"gonal, houy scutes, firml}" 

 joined at their edges, and with distinct teeth in the jaws. There is but 

 one family, the fMraeiida^^ a singular offshoot from the Sclerodermi. 

 [oGTpaKov. a hard shell, like that of an oyster; depfAa^ skin.) 



Family IV. OSTRACIID.E. 



TRUNK FISHES. 



Bod}^ short, cuboid, triquetrous or pentagonal, covered by a cara- 

 pace formed of tirmh" united polygonal bony plates, the jaws, bases 

 of the fins, and caudal peduncle free and covered l)y smooth skin. 

 Mouth small; each jaw with a single series of long, narrow teeth. 

 Maxillaries and premaxillaries firmly united. Gill opening a nearly 

 vertical slit, below and behind the eye. Dorsal fin single, short, with- 

 out spine; anal short, similar to dorsal; caudal rounded; no ventral 

 fins; vertebrffi 14, the anterior 9 elongate, the last 5 extremeh' short; 

 no ribs. All are species 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 gathering of tropical curiosities began. 



a. Carapace forming a continuous bridge behind the anal fin; ventral surface not 



carinate; caudal rays 10. 



h. Body 4-angled, sometimes with an additional median dorsal spine.. Os/rado??, 16 



act. Carapace open below, behind the anal fin; carapace 6-ridged, a ridge along the 



middle of each side Aracana, 17 



16. OSTRACION Linnseus. 



Ostracion Linn^us, Syst. Nat., 10th ed., 1758; p. 330 (many species; first restricted 



by Swainson to 4-angled forms, eubicus taken as type). 

 Teirosomws SwAiNSON, Classn. Fish., II, 1839, p. 323 {lurritus). 

 Cibotion Kaup, Wiegmann's Archiv. Natur., 1855, p. 214 (eubicus). 

 Ladoria Jordan and Fowler, new subgenus {cornvlKfi). 



Trunk fishes with the carapace closed behind the anal fin; carapace 

 with or without frontal and abdominal spines; dorsal rays 9 or 10; 

 caudal rays always 10; lateral ridges developed; median dorsal ridge 

 undeveloped or else raised with a sharp spine, and the body is there- 

 fore l-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. We think, with 

 Dr. Goode, that the shape of the carapace affords "the most reliable 



^ This name should be used for the trunk fishes, and not for the OMracophon or 

 extinct mailed allies of Pterlchlhyx, for which it has been so frequently taken. 



