FRESH-WATER FISHES OF SIAM, OR THAILAND 555 



rosy body with. 7 or 8 dark somewhat oblique transverse bands, with 

 large, irregularly shaped and disposed ocelluslike rosy or pearly spots, 

 surrounded by a very narrow dark line, and on the membranes of both 

 dorsal fins numerous elliptical ocelli consisting of a mauve center, a 

 narrow white ring, and a still narrower dark outer line. 



The Thailand records for this species are seven specimens now in the 

 U. S. National Museum, 7.6 to 9.9 cm, long, taken in the Gulf of Siam 

 at Koh Kahten in May 1931, and six at Koh Pa-ngan in July 1931. 

 The fish has been found also at Koh Samui, in the same section of the 

 Gulf of Siam. A specimen from Koh Pa-ngan, examined at the Royal 

 Natural History Museum in Leiden by Dr. F. P. Koumans, was pro- 

 nounced by hun as agreeing with Bleeker's type. 



CRYPTOCENTRUS GYMNOCEPHALUS (Bleeker) 



Gobius gymnocephalus Bleekeb, 1853 (78), p. 473 (Batavia). 

 Cryptocentrus gymnocephalus Smith, 1933a, p. 82 (Koh Sichang). 



Described from two specimens, 11.7 and 14 cm. long, from Batavia, 

 Java, this species seems to have been encountered infrequently. 

 Bleeker's voluminous writings contain a single subsequent reference to 

 the occurrence of the fish, at Hong Kong (1873 [425] , p. 128) . 



One specimen 12.1 cm. long was taken at Koh Sichang in June 1929. 

 It was compared by Dr. Koumans with Bleeker's types in the Royal 

 Natural History Museum in Leiden and found to be in agreement. 



Family PERIOPHTHALMIDAE: Mudskippers 



These gobies are familiar creatures on mud flats tliroughout tropical 

 and temperate seas of the Oriental region and Oceania. The pectoral 

 fins, with elongated and well-developed muscular base, are used for 

 locomotion out of water and they enable the fishes to move rapidly 

 and to make surprising leaps. The large eyes, placed very close to- 

 gether at the top of the head, are on short stalks and may be elevated 

 for making observation and withdrawn flush with the surface. 



The family as herein considered comprises the closely related genera 

 Periophthalmus and Periophthalmodon^ both represented in Thailand. 

 Some authors place in this family the genera Boleophthalmus and 

 Scartelaos which, in the present catalog, are assigned to another family 

 on the basis of horizontal teeth in the lower jaw, fully united ventral 

 fins at all stages of growth, short first dorsal fin, very long second dorsal 

 and anal fins, and other characters. 



The two Thailand genera may be differentiated as follows : 



lo. Spines in first dorsal fin 10 to 15 ; ventral fins united only at base ; teeth in 

 both jaws in a single row ; scales ctenoid, minute, 75 to 100 in lengthwise 

 series _ Periophthalmus 



