=The Jawfishes: Opisthognathidæ, etc.=—The _Pseudochromipidæ_ are marine-fishes of the tropics with the lateral line interrupted, and with a single dorsal. They bear some resemblance to _Plesiops_ and other aberrant _Serranidæ_. [Illustration: FIG. 297.—_Gnathypops evermanni_ Jordan & Snyder. Misaki, Japan. ] [Illustration: FIG. 298.—Jawfish, _Opisthognathus macrognathus_ Poey. Tortugas, Fla. ] Very close to these are the _Opisthognathidæ_ or jawfishes with a single lateral line and the mouth very large. In certain species of _Opisthognathus_, the maxillary, long and curved, extends far behind the head. The few species are found in warm seas, but always very sparingly. Some of them are handsomely colored. =The Stone-wall Perch: Oplegnathidæ.=—A singular group evidently allied to the _Hæmulidæ_ is the family of _Oplegnathidæ_. In these fishes the teeth are grown together to form a bony beak like the jaw of a turtle. Except for this character, the species are very similar to ordinary grunts. While the mouth resembles that of the parrot-fish, it is structurally different and must have been independently developed. _Oplegnathus punctatus_, the "stonewall perch" (ishigakidai), is common in Japan, as is also the banded _Oplegnathus fasciatus_. Other species are found in Australia and Chile. [Illustration: FIG. 299.—_Opisthognathus nigromarginatus._ India. (After Day.) ] =The Swallowers: Chiasmodontidæ.=—The family of swallowers _Chiasmodontidæ_, is made up of a few deep-sea fishes of soft flesh and feeble spines, the opercular apparatus much reduced. The ventrals are post-thoracic, the rays I, 5, facts which point to some affinity with the _Opisthognathidæ_, although Boulenger places these fishes among the _Percesoces_. _Chiasmodon niger_, the black swallower of the mid-Atlantic, has exceedingly long teeth and the whole body so distensible that it can swallow fishes of many times its own size. According to Gill: [Illustration: FIG. 300.—Black Swallower, _Chiasmodon niger_ Johnson, containing a fish larger than itself. Le Have Bank. ]