330 



TRANSACTIONS OF THE AMERICAN PHILOSOPHICAL SOCIETY 



Sioux Indian chief with a feather head-dress. Aploactis (Fig. 2085) supplies a structural 

 starting-point. 



Hexagrammids. — In these more or less cod-like fishes, the skull (Fig. 209) is entirely 

 devoid of spines, but relationship with the scorpaenoid group is definitely indicated by the 

 presence of a complete suborbital stay. The family are also more specialized than the 

 Scorpaenidae in the marked increase in number of the vertebrae and their relative de- 

 differentiation. Externally the Hexagrammidae differ widely from the other scorpaenoids 

 in their smooth, more or less cod-like appearance. Possibly they may be related to the 

 ancestral Cottidae through Ophidion (Fig. 210). 



B 



Rata ecus 



Aploacti 



Fig. 208. A. Aploactis milesii. B. Patacus. After McCulloch. 



In the genus Platycephalus, which is the type of the family Platycephalidae, the skull 

 (Fig. 211) is elongate, more or less flattened; the eyes are directed partly upward. Leighton 

 Kesteven (1926, pp. 208-218) gives excellent figures of the skull of Platycephalus mar- 

 moratus, which seems to be a relatively primitive species, not very far from the central 

 scorpaenoid type. The suborbital stay extends to the backwardly-inclined preopercular, 

 which bears two small spikes apparently homologous with the two main ones in Scorpana. 

 The body-form as a whole (Day, .1878-1888, Pis. LIX, LX) suggests relationships with the 

 Cottidae and Agonidae, near which Boulenger (1910, p. 699) locates this family. 



Hemitripterus is classed among the Cottiformes but its skull is derived from the Scor- 

 pana type; the skull top is broad with thin translucent bones and blunted spikes; on the 

 preopercular only the upper pair of spikes persist (Fig. 2145). 



