the prefrontals tend to be separated mainly by the fron- 

 tals, while in Fugu it is variously mostly by the frontals 

 or about half by the ethmoid and half by the frontals. In 

 Torquigener the two species examined have the prefron- 

 tals separated about half by the ethmoid and half by the 

 frontals. Again, however, this is more a simple matter of 

 how broadly the frontals cover the dorsal surface of the 

 ethmoid rather than a characteristic of fundamental im- 

 portance. 



In Ephippion, Arothron, Monotreta, Chelonodon, Ca- 

 rinotetraodon, and Tetraodon the ethmoid tends to form 

 a greater proportion of the prefrontal separation than 

 does the frontal, and a greater proportion than in most 

 (but not all) species of the genera with two nostrils. In 

 Arothron, for example, most species have the prefron- 

 tals separated almost entirely by the ethmoid, but in one 

 species {armilla) the prefrontals are separated almost ex- 

 actly half and half by the ethmoid and frontals. In Tetra- 

 odon, Carinotetraodon, and Chelonodon the separation 

 is mostly if not entirely by the ethmoid, while in Mono- 

 treta the separation in most species is about half and half 

 by the ethmoid and frontals, but almost exclusively by 

 the frontals in one species (gularis). 



Fraser-Brunner said that Arothron (as the Arothroni- 

 nae) had the sphenotics not laterally expanded beyond 

 the rest of the orbital roof formed by the frontals, the 

 orbital roof strongly arched, the prefrontal curved down 



Figure 270.— Dorsal views of skulls of: left, 

 Tetraodon lineatiu, 222 mm SL, French Equi- 

 torial Africa; right, T. mbu, 47.7 mm SL, Congo. 



before the eye and enclosing the olfactory foramen, the 

 ethmoid relatively narrow and compressed, and a single 

 lateral line, while in Ephippion, Monotreta, Chelono- 

 don, Carinotetraodon, and Tetraodon (the Tetraodon- 

 tinae) the sphenotics are laterally expanded beyond the 

 frontal as a prominent lobe, the orbital roof is not much 

 arched, the prefrontal not curved down before the eye 

 and not enclosing the olfactory foramen, the ethmoid 

 broad and a lower lateral line present which joins the up- 

 per. 



It is true that the approximately six species of Aroth- 

 ron form a distinctive subgroup of Indo-Pacific puffers 

 that is recognizable by external features alone: by a cer- 

 tain difficult to describe sameness in configuration 

 (short, heavy bodies), as well as by the normally bifid 

 tentacle with pitted inner surfaces and the single lateral 

 line. In the relatively normal members of Arothron 

 (represented in species studied here by hispidus, nigro- 

 punctatus, stellatus) the sphenotics are only slightly if at 

 all expanded beyond the edge of the frontal, primarily 

 because the frontal is exceptionally wide at the posterior 

 region of the orbit (about 3 times as wide as more poste- 

 riorly in front of the supraoccipital), and the orbital roof 



