over the fossa, but the wings are relatively shorter in iner- 

 mis and scleratus and do not meet the posterodorsal sur- 

 face of the pterotic and thus only incompletely roof 

 over the fossa. The lesser development of the wings in m- 

 ermis and scleratus would seem to be the most generaliz- 

 ed condition. The posterolateral region of the pterotic is 

 directed more or less laterally in laevigatas, lunaris, 

 scleratus, and spadiceus, but it is prolonged postero- 

 laterally in inermis and, especially greatly so, in lago- 

 cephalus. The ventral flange along the middle of each 

 side of the rear of the skull formed by the pterotic and ex- 

 occipital is much longer in lagocephalus than in the other 

 species. A larger portion of this flange in Lagocephalus is 

 formed by the exoccipital than in most, but not all, other 

 tetraodontids (see, for example, illustration of Tetraodon 

 lineatus). 



The shape of the anterior portion of the frontals in 

 Lagocephalus is probably of as much phylogenetic in- 

 terest as is that of the posterolateral wing development. 

 In scleratus the frontal tapers gradually and evenly 

 toward the front and is of moderate width, this being 

 similar to the condition in the more generalized species of 

 Sphoeroides. In inermis the frontal is somewhat broader 

 over the orbit than in scleratus and abruptly begins to 

 taper to a point at the rear of the prefrontals. In lunaris 

 the configuration is much the same as in inermis, except 



Figure 259.— Dorsal views of skulls of: 



A, Sphoeroides anguaticepa, 172 mm SL. Galapagos; 



B, S. epengleri, 92.8 mm SL, Nicaragua; 



C, S. maculattu, 179 mm SL, Virginia. 



that there is greater abruptness in the tapering, the 

 length of the broad region of the frontal above the orbit is 

 shorter, and the lateral edge of the prefrontal forms a 

 proportionally greater amount of the edge of the orbit. In 

 laevigatus, lagocephalus, and spadiceus the frontal is 

 even wider over the orbit than in lunaris, and is similarly 

 abruptly tapered, with the prefrontal forming a large 

 part of the relatively straight edge of the orbit. Since a 

 gradually tapered frontal of moderate width, as found in 

 the ancestral triodontids, can be considered the 

 generalized condition, the above series is one of in- 

 creasing specialization. The most generalized species in 

 this respect, scleratus, is also one of the two species with 

 the most generalized condition of the posterolateral wing 

 of the frontal, while the other species {inermis) with a 

 generalized posterolateral wing has the next most 

 generalized condition of anterior tapering. 



The extreme posterolateral region of the dorsal surface 

 of the pterotic in most species of Lagocephalus is uprais- 

 ed into a flange, with which the posterolateral wing of the 

 frontal articulates in lunaris, spadiceus, and laevigatus. 



