FRESH-WATER FISHES OF SIAM, THAILAND 41 



Paknam in 1901 was 6 meters long and so unwieldy that it could not be 

 taken into the fishermen's boat ; its saw, deposited in a local joss house 

 and examined in July 1923, was 118 cm. long from the basal pair of 

 teeth and 25 cm. broad ; the teeth numbered 18 on each side, and the 

 largest were 6 cm. long. 



In the Mahaniiddee River in India this fish, according to Day, as- 

 cends at least 40 miles from the sea, far beyond the influence of the 

 tides and salt water. 



Family DASYATIDAE: Stingrays 



Genus DASYATIS Rafinesque 



Dasyatis Rafinesque, Caratteri animali piante Sicilia, p. 16, 1810. (Type, Das- 

 yatis it jo Rafinesque.) 



This world-wide genus of stingrays is represented in Thailand by 

 two species that regularly frequent fresh water, besides a number of 

 others found only in salt or brackish water. The general vernacular 

 name for these fishes is pla kaben, sometimes contracted to pla ben, the 

 different species being distinguished by qualifying adjectives. 



la. Tail with a long, deep cutaneous fold on its ventral surface, none on dorsal 

 surface ; 5 long papillae inside mouth on lower jaw ; disk broader than long, 



its anterior angle obtuse sephen 



16. Tail without a cutaneous fold on either ventral or dorsal surface; 2 papillae 

 inside mouth on lower jaw; disk longer than broad, its anterior angle 

 acute bleekeri 



Various other rays listed by Fowler (1935a, 1937) from Bangkok and 

 Paknam are regarded as market specimens caught in the Gulf of Siam 

 and therefore excluded from the scope of this catalog. 



DASYATIS SEPHEN (Forsk&l) 



Raja sephen Fobskal, 1775, pp. viii, 17 (Djedda, Lohaja, Red Sea). 



This well-known stingray of the Indian Ocean and Indo-Australian 

 Archipelago is common on the coasts of Thailand and occurs regularly 

 in fresh water. It is found up the Menam Chao Phya for at least 20 

 miles above Bangkok. In the inner lake of the Tale Sap it is quite 

 common at times and produces young in the strictly fresh waters of 

 that "inland sea." Two specimens collected on July 5, 1929, were a 

 male 71.5 cm. long with disk 18.5 cm. wide and a female 73 cm. long with 

 disk 20 cm. wide, which were born under observation from a fish 59 cm. 

 broad, 52 cm. long to base of tail, and 118 cm. in total length; the young 

 emerged tail first closely rolled on their long axis. 



This ray attains a large size in the local salt waters. One measured 

 at Chumporn on the Gulf of Siam, September 25, 1923, weighed 61 

 kilograms and was 252 cm. in total length, with the body 109 cm. long 



