+ ACANTHOPTERYGII. 
Fam. 2. GOBIESOCIDE. 
The Cling-fishes are small marine fishes, easily recognizable by the naked body, the 
short dorsal and anal fins without spinous rays, the widely separated ventral fins, which 
are jugular in position, and by the small gill-openings. They have an adhesive ventral 
disc, by means of which they adhere to stones or shells. They are usually found 
between tide-marks; but Pellegrin (Bull. Mus. Paris, vii. 1901, p. 206) has recorded 
that a species which he identifies with Gobiesor adustus, Jord. & Gilb., originally 
described from Mazatlan, is common in rapid streams near Tepic, Jalisco, and in the 
Rio Grande de Santiago. 
Fam. 3. GOBIIDA. 
A large family, chiefly marine, but with representatives in the fresh waters of all 
parts of the world. The Gobiide may easily be distinguished from other Acantho- 
pterygians found in the rivers of Mexico and Central America by the following 
peculiarities :—The spinous portion of the dorsal fin is composed of a few slender 
non-articulated rays ; the anal fin is preceded by a single slender spine; the pectoral is 
symmetrical and has a broad, subvertical base; the ventrals, inserted below the base of 
the pectorals, consist each of a short feeble spine and of five branched rays; the 
gill-openings are restricted, the gill-membranes being more or less broadly attached to 
the isthmus. 
Synopsis of the Genera represented in the Fresh Waters of Mexico and Central America. 
I. Ventral fins separate. 
Jaws with bands of pointed teeth ; vomer with teeth; lower jaw pro- 
jecting ; gill-openings extending forward to below the eye. . . . 1. PHiLypnus.. 
Jaws with bands of pointed teeth; palate toothless; lower jaw pro- 
jecting ; gill-openings not extending forward to below the eye . . 2. Exzorris. 
Jaws with bands of movable, slender teeth with truncate apices; palate 
toothless; jaws equal anteriorly; gill-openings not extending 
forward to below theeye . . . . . . . . . . . . . . 8 Dormirator. 
II. Ventral fins united to form a disc. 
A. Two dorsal fins. 
1. Each jaw with a series of numerous slender teeth, those in the lower 
jaw horizontal and sometimes hidden by the gum; lower jaw with 
an inner series of a few erect conical teeth. . . . . . . . . 4 Sicyprum. 
2. Jaws with bands of pointed teeth. 
Two or three fleshy flaps on the anterior edge of pectoral arch, 
projecting into the gill-cavity . . . . . . . . . . . 5. CHonopHorus. 
No dermal flaps on the pectoral arch. . . . . . . . . . . 6. Gosrus. 
B. Asingle dorsal fin. 2. 2. 2. 2. 2... ew we ee «7. Gostorpes. 
