The Gobies form a large group. They are mostly small fishes, carnivorous and marine. Some are found in estuaries and rivers; two species are known to descend below the 100-fathom line. The majority are littoral, and the typical forms with united ventral fins are easily distinguished.

Key to the South African families.

1. Ventral fins completely separate .

Eleotridae.

2. Ventral fins united either at base only, or completely, forming a sucking disc Gobiidae.

Fam. 1. ELEOTRIDAE.

Ventral fins separated, their bases not contiguous. Two dorsal fins. Soft dorsal and anal free from caudal, which is rounded. Pectorals well developed, upper rays without free filaments. Teeth in a single row, or in bands, with or without canines. Gill-rakers long or reduced. Scales cycloid or ctenoid.

Gen. ELEOTRIS Gron.

1754. Gronovius, Mus. Ichthyol., p. 16.

1763. Id., Zooph., p. 83.

1801. Bloch Schneider, Syst. Ichthyol., p. 65.

1918. Fage, Dan. Ocean. Exp., vol. ii, A 3, p. 99 (post-larval stages). Teeth small, conical, the outer series enlarged, with or without canines; none on vomer. Scales moderate or small, cycloid or ctenoid. Gill-rakers more or less reduced. Pseudobranchiae more or less reduced. No barbels.

This genus has been variously subdivided, but so far as the South African fauna is concerned, it is quite unnecessary.

Coasts and rivers between the tropics. Boulenger (Freshwater Fishes of Africa, vol. iv, 1916) records 14 species from African rivers.

Key to the South African species.

1. A strong spine at angle of preopercle, concealed beneath the skin. Scales: 1.ser. 60-78

2. No preopercular spine.

a. Body strongly compressed

b. Body feebly compressed.

i. Scales: 1.ser. 35-42

ii. Scales: 1.ser. 28 .

fusca.

.butis.

ophiocephalus.

delagoensis.

Eleotris fusca (Bl. Schn.).

1801. Bloch Schneider, Syst. Ichthyol., p. 453.

1878-88, Day, Fish. India, p. 313, pl. lxv, fig. 7.

1916. Boulenger, Freshwater Fish. Africa, vol. iv, p. 21, fig. 14 (references).

1917. Gilchrist and Thompson, Ann. Durban Mus., vol. i, pt. 4, p. 401 (references).

Body feebly compressed. Depth 4-43, length of head 3-31, in length of body. Head broader than deep. Eye 4 (young)–7 in length of head, 1-2 in interorbital width, equal to or rather less than snout. Maxilla extending to below centre or posterior third of eye. No canine teeth. A strong spine at angle of preopercle, projecting downwards and forwards, concealed beneath the skin. D VI+I 8. A I 8. P 18. Scales ctenoid: 1.ser. 60-78; tr.ser. 17-21. Head scaly, except on snout and chin. Gill-rakers 10 on lower part of anterior arch, very short. Pseudobranchiae reduced.

Length.-Up to 260 mm.

Colour.-Dark brown or blackish, vertical fins mottled or banded. Locality.-Natal and east coast of Africa.

Distribution.-Indo-Pacific.

*Eleotris butis (Ham.-Buch.).

1822. Hamilton-Buchanan, Fish. Ganges, p. 57. 1878-88. Day, Fish. India, p. 315, pl. lxvii, fig. 3.

1916. Boulenger, Freshwater Fish. Afr., vol. iv, p. 10, fig. 6 (references).

Body strongly compressed. Depth 41-5, length of head 23-3, in length of body. Head much depressed, broader than deep. Eye 5-61 in length of head, (young) or length of snout, 1-13 in interorbital width. Maxilla extending to below anterior third or centre of eye. No canine teeth. No preopercular spine. D VI+I 8. AI 8. Scales ctenoid 1.ser. 29-32; tr.ser. 10-11. Head almost entirely scaly, with finely serrated ridges above and a groove on each side behind eye. Length.-Up to 135 mm.

Colour. Brownish, soft dorsal and caudal spotted, anal with dark margin edged with white, 1st dorsal dark, a light or scarlet spot divided by a black mark on base of pectoral.

Locality.-Mozambique.

Distribution.-East coast of Africa, Indian seas, Malay Archipelago.