FRESH-WATER FISHES OF SIAM, OR THAILAND 573 



In some species the muscular tissue and abdominal viscera are ex- 

 tremely poisonous, and in Thailand, as in other parts of the world, 

 deaths have occurred when human beings have eaten such fishes. The 

 poison, an alkaloid related to the deadly principle found in certain 

 mushrooms, acts quickly and death may ensue in 1 to 3 hours. 



Four genera are known to Thailand as follows : 



la. Each nostril with 2 openings in a short tube or papilla Sphoeroides 



1&. Each nostril with a simple imperforate cavity surrounded by a tube or pro- 

 vided with a tentacle. 

 2a. Dorsal and anal fins long, with 25 to 36 rays and 22 to 29 rays respectively ; 



coloration plain Chonerhinus 



2&. Dorsal and anal fins short, with less than 15 rays; coloration various. 

 3a. Each nostril with a short tube, whose margin is divided into flaps or 



fringe ; back and abdomen spinous, middle of side smooth Chelonodon 



36. Each nostril with a bifid tentacle ; body more or less spinous Tetraodon 



Genus SPHOEROIDES Anonymous 



Sphoeroides (author anonymous), Allg. Lit. Zeit., 1798, col. 676. (Type, Tetrodon 

 spenffleri Bloch.) 



SPHOEROIDES LUNARIS (Bloch) 



Tetrodon lunaris Bloch, in Schneider, ISOl, p. 505 (Sea of Malabarico). 



Tetraodon lunaris Bleekee, 1865 (356), p. 172 (Siam). 



Lagocephalus lunaris Fowoat, 1937, p. 264 (Pitsanulok, Tachin, Paknam). 



This widely distributed and common species of eastern and southern 

 Asia, the Philippines, and the Indo-Australian Archipelago is essen- 

 tially marine, but it enters the mouths of rivers and, exceptionally, 

 appears to go far up streams. A noteworthy record for Thailand, 

 where the species is abundant in the coastal waters, is for the Nan River 

 at Pitsanulok (Fowler, 1937). 



A length of 25 cm. is attained. 



Genus CHONERHINUS Bleeker 



Chonerhinus Bleekee (301), Atlas ichthyologique, vol. 5, p. 49, 1865. (Type, 

 Chonerhinus naritus Bleekev=Tetraodon naritus Richardson.) 



This genus is characterized hj a well-compressed, rather stout body, 

 many-rayed dorsal and anal fins, a single imperforate nostril on each 

 side surrounded by a rather high rim, small spines on abdomen and 

 sides, and plain coloration (golden yellow, golden green). The two 

 local species, very similar, may be distinguished by the features indi- 

 cated as follows : 



la. Abdominal spines not extending upward beyond the level of the pectoral fins ; 



dorsal rays v, 20 or vi, 20 ; anal rays iii or iv, 19 or 20 __modestus 



16. Abdominal spines extending upward beyond pectorals both anteriorly and 



posteriorly ; dorsal rays iv or v, 31 or 32 ; anal rays ii or iii, 26 naritus 



