197] OSTEOLOGY OF LORICATI — GUTBERLET 27 



SUMMARY 



Since Ophidon and Hexagrammos belong to the same family, 

 Hexagrammidae, one might expect something of a similarity in their 

 osteology and also more marked differences between Scorpio nichthys, 

 belonging to the family Cottidae, and Ophidon. From a study of these 

 forms I find that there are more differences between Ophidon and 

 Hexagrammos than between Ophidon and Scorpio nichthys. 



Some of the differences between Ophidon and Hexagrammos are, — 



1. The dorsal surface is more rounded in the latter. 



2. The supraoccipital possesses a conspicuous spine-like crest in the 

 median line which entirely separate the parietals in Hexagrammos. 



3. Foramina are present in the dilatator fossa in Ophidon but 

 absent from Hexagrammos. 



4. In Hexagrammos there are no nasal pit depressions on the eth- 

 moid and prefrontal. The ethmoid is but slightly keeled and the anterior 

 portion of the prefrontal possesses a lateral facet. 



5. In Ophidon the frontal is thick and porous, but in Hexagram- 

 mos, thin and smooth, with a single flange and a single groove on the 

 ventral surface. 



6. The sphenotic does not form part of the posterior edge of the 

 orbit in Hexagrammos. 



7. In Ophidon only a small part of the anterior hyomandibular facet 

 is formed by the prootic, while in Hexagrammos this bone forms at least 

 half of it. Also there is a conspicuous lateral prootic process below the 

 hyomandibular facet in the latter genus. 



8. In Ophidon the hyomandibular shank extends ventro-caudad 

 while in Hexagrammos it extends ventro-cephalad, placing the quadrate 

 further cephalad. 



9. In Hexagrammos the preopercular spines and ridges found in 

 Ophidon are absent, and the bone itself occupies a more ventral position. 



10. Relatively, the mandible is twice as long in Ophidon as in Hex- 

 agrammos and the dentary possesses no lateral ridge or cavity, nor a me- 

 sial flange on the ventral surface. 



11. A marked difference is found in the teeth in Ophidon and 

 Hexagrammos. Both canine and villiform are found in the former but 

 only the villiform in the latter. 



