lower one always better developed than in the traces of it 

 sometimes found in Sphoeroides and Guentheridia, even 

 though the lower line may not run the full length of the 

 caudal peduncle (see illustration of Torquigener pleuro- 

 stictus). Possible exceptions are Amblyrhynchotes 

 piosae, in which the exceptionally long spines mostly ob- 

 scure the lateral line, so that in the single alcohol- 

 preserved specimen examined I am unable to find any 

 lateral line at all on the caudal peduncle, and A. richei, 

 in which I cannot find a lower lateral line in any of the 10 

 alcohol preserved specimens examined, although Le 

 Danois (1959:172) showed it as present. A distinctly up- 

 raised horizontal ridge of skin is present ventrolaterally 

 along the caudal peduncle in all species of Logo- 

 cephalus, in most species of Torquigener (absent in 

 pleurostictus) and Fugu (absent or only weakly 

 developed in chrysops), in at least some species of 

 Amblyrhynchotes (honckenii and hyselogenion) and 

 Sphoeroides (e.g., see illustrations of lobatus, testudi- 



neus, and dorsalis), but it is absent in Guentheridia and 

 Colomesus. The presence or absence of this ridge is of 

 very limited systematic interest at the generic level, 

 while the presence or absence of a second, lower, lateral 

 line is more variable within certain genera than previous- 

 ly thought. 



In those genera with a single nostril or a nasal tentacle, 

 there is a single lateral line in Arothron, while in 

 Chelonodon and Monotreta the upper lateral line nor- 

 mally curves ventrally to join the lower lateral line in the 

 region above the anal fin, the lower line continuing pos- 

 teriorly to the tail as well as anteriorly to the abdominal 

 region from the point of juncture with the upper lateral 

 line. Tetraodon has some species with basically the same 

 arrangement as in Chelonodon and Monotreta (see illus- 

 trations of T. lineatus and T. mbu), but in at least one 

 species (see illustration of T. miurus) there seems to be 

 no lower lateral line, the upper line continuing directly 

 onto the tail, while in another (see illustration of T. 



Figure 210.— External features of other 

 representative tetraodontid genera: 



A, Sphoeroides nephelus, upper left, nasal 

 region as seen externally (far left) and 

 olfactory lamella as seen with front of 



nasal sac removed, and, lower left, scales 

 from upper middle region of body; 



B, S. testudineua, upper left, nasal region 

 as seen externally (olfactory lamella, if 



present, indistinct in specimen examined), 



and, lower left, scales from upper middle 



region of body; C, S. dorsalis, upper left, nasal 



region as seen externally (far left) and 



olfactory lamella as seen with front of 



nasal sac removed, and, lower left, scales 



from upper middle region of body; D. S. lobatus, 



upper left, nasal region as seen externally 



(olfactory lamella, if present, indistinct 



in specimen examined), and, lower left, 



scales from upper middle region of body 



(larger markings on rear of body, and one 



on dorsum, represent flaps rather than 



scales); E. S. pachygaster. lower left, nasal region 



as seen externally and, upper left, 



olfactory lamellae as seen with front 



of nasal sac removed, showing more 



lerous lamellae than in other species 



of Sphoeroides (scales absent). 



291 



