less dorsoventrally compressed into a plate. The frontal 

 in Ephippion is about as laterally expanded over the 

 middle of the orbit as in Tetraodon, but it tapers some- 

 what more evenly and gradually to a point anteriorly 

 than in Tetraodon. In Ephippion the prefrontals are 

 separated about half and half by the ethmoid and fron- 

 tals, while in Tetraodon they are mostly separated by the 

 ethmoid. The ethmoid of Ephippion is slightly less wide 

 than in Tetraodon. The vertebrae in Ephippion are 8 + 

 12 = 20, while in the three species of Tetraodon for which 

 vertebral counts are presented the range is 8 + 9 = 17 

 to 8 + 11 = 19. In £p/iippion there are several tritura- 

 tion teeth in a single row to either side of the midline in 

 the upper jaw, but none in the lower; while in the two 

 species of Tetraodon cleared and stained, there are no 

 trituration teeth in either jaw. In both Ephippion and 

 Tetraodon there are minute teeth on the first pharyngo- 

 branchial and the dorsal flange of the parasphenoid in 

 the orbit meets the frontals, but there are no remnants of 

 the dorsal roof of the myodome, no interhyal, and only a 

 single hypohyal. 



Until recently, the categories Monotreta, Chelonodon, 

 and Tetraodon were badly in need of revision. They are 

 defined, as subgenera of Tetraodon, by Fraser-Brunner 

 (1943) entirely on nasal and scale pattern characteristics 



Figure 273.— Dorsal views of skulls of: 1 

 Monotreta gularis, 46.8 mm SL, Burma; 

 right. M. leiurus. 61.5 mm SL, Thailand. 



that are less than adequate. These categories have nearly 

 always been used at the generic level, for failure to do so 

 leaves Tetraodon an unmanageable assemblage of 

 numerous species, some obviously far more closely 

 related than others. The use of these three categories also 

 presents problems, which will probably only be solved 

 when each of the species not discussed here has had its 

 external and internal features compared with those de- 

 scribed here. Dekkers (1975) has provided an excellent 

 revision of these Asiatic and mainly freshwater puffers 

 based on external characters, placing them all in one 

 genus, with five unnamed subcategories for 15 species, 

 two of which (erythrotaenia and waandersii) contain sin 

 gle species not studied here. For purposes of compara 

 five discussion in this monograph, Tetraodon, Chelono- 

 don, and Monotreta are recognized at the generic level 

 In Monotreta (nasal apparatus a tube with a single 

 nostril, the aperture of the tube with or without lips or 

 flaps) three of the four species studied are rather similar 

 to one another, and possess one feature unique to the 



