CHAPTER XXVI
GOBIOIDEI, DISCOCEPHALI, AND TÆNIOSOMI
Suborder Gobioidei, the Gobies: Gobiidæ.—The great family of Gobiidæ, having no near relations among the spiny-rayed fishes, may be here treated as forming a distinct suborder.
The chief characteristics of the family are the following: The ventral fins are thoracic in position, each having one spine and five soft rays, in some cases reduced to four, but never wanting. The ventral fins are inserted very close together, the inner rays the longest, and in most cases the two fins are completely joined, forming a single roundish fin, which may be used as a sucking-disk in clinging to rocks. The shoulder-girdle is essentially perch-like in form, the cranium is usually depressed, the bones being without serrature. There is no lateral line, the gill-openings are restricted to the sides, and the spinous dorsal is always small, of feeble spines, and is sometimes altogether wanting. There is no bony stay to the preopercle. The small pharyngeals are separate, and the vertebræ usually in normal number, 10 + 14 = 24.
The species are excessively numerous in the tropics and temperate zones, being found in lakes, brooks, swamps, and bays, never far out in the sea, and usually in shallow water. Many of them burrow in the mud between or below tide-marks. Others live in swift waters like the darters, which they much resemble. A few reach a length of a foot or two, but most of the species rarely exceed three inches, and some of them are mature at half an inch.
The largest species, Philypnus dormitor, the guavina de rio, is found in the rivers of Mexico and the West Indies. It reaches a length of nearly two feet and is valued as food. Unlike most of the others, in this species there are teeth on the vomer. Other related forms of the subfamily of Eleotrinæ, having the ventral fins separate, are Eleotris pisonis, a common river-fish everywhere in tropical America; Eleotris fusca, a river-fish abounding from Tahiti and Samoa to Hindostan; Dormitator maculatus, the stout-bodied guavina-mapo of the West Indian regions, with the form of a small carp. Guavina guavina of Cuba is another species of this type, and numerous other species having separate ventrals are found in the East Indies, the West Indies, and in the islands of Polynesia. Some species, as Valenciennesia strigata of the East Indies and Vireosa hanæ of Japan, are very gracefully colored. One genus, Eviota, is composed of numerous species, all minute, less than an inch in length. These abound in the crevices in coral-heads. Eviota epiphanes is found in Hawaii, the others farther south. Hypseleotris guntheri, of the rivers and springs of Polynesia, swims freely in the water, like a minnow, never hugging the bottom as usual among gobies.
Fig. 412.—Guavina de Rio, Philypnus dormitor (Bloch & Schneider). Puerto Rico.
Fig. 413.—Dormeur, Eleotris pisonis Gmelin. Tortugas, Fla.