of the Fisher ij Board for Scotlatid. 277 



Upper Pharijriijecds (up. Phr.). 



Con, Fig. 24, PI. XI.: Saithe, Fig. 18, PI. XL: Lythf,, Fi- 21, PI. IV. 



The main point uf ditt'ereuce between the upper pharyngeals of the 

 three species con.sists in the comparative size of the teeth. They are very 

 small in the saithe, much larger in the lythe, and very large in the cod. 



Lower I'haryngeals (1. Thr.). 



Cod, Fig. 25, PI. XI. : Saithe, Fig. 19, PI. XL: Lythe, Fig. 21rt, PI. IX 



The teeth in the lower [)haryngeals are riuialler than those in the upper 

 pharyngeals. The difference in the size ot the teeth between the bone.s 

 of the saithe and lythe is not very striking ; in both these species the 

 teeth are very much less than those in the cod. Li the proximal portion 

 of the toothed area in tlie lythe the teeth are considerably larger than 

 the other.-?, and than the teeth in a sirailirly sized saithe bone. 



Dermal Bones. 



The dermal bones have been described recently by Cole* in connection 

 with his work on the sensory canals. 



Xa^al (N.). 



Cod, Fig. 26, PI. X. : Saithe, Fig. 1, PI. X. : Lvtiie, Fig. 1, PI. IV. 



In the saithe and lythe the nasal is in large part membranous ; in the 

 cod it is almost wholly ossified. The anterior and hind borders in all 

 three are membranous ; in the saithe and lythe the membranous anterior 

 portion is fully one-fourth of the total length of the bone. The nasal is 

 depressed along its longitudinal axis ; this furrow lodges the nasal part 

 of the supraorbital sensory canal. Processes from either side of the 

 anterior half of the bone approach one another, and form a partial bridge 

 over the canal. In the cod the groove in this bone is more defined than 

 in the other two species. 



Pneorbital or Lachrymal (pr. < h-.). 



Cod, Fig. 27, PI. X. : Saithe, Fig. 2, PI. X. : Lythe, Fig. 4, PI. IV. 



The pragorbital is a triangular bone, which articulates by its hind 

 superior corner with the prefrontal, and by its anterior end with the 

 nasal. 



In the cod and lythe the superior edge of the bone is concave, while in 

 the saithe it is convex in outline. The prseorbital of the lythe is shorter 

 and broader than those of the saithe and cod. The hind edge of this 

 bone in the saithe slopes more posteriorly than in the lythe and cod. 



The prworbital has two prominent grooves which are formed b}'^ over- 

 hanging bone plates. The two grooves, which are in the same line, are not 

 continuous, but are usually separated by an interval at about the middle 

 of the bone. Occasionally there is a secondary narrow plate developed 



* Observations on the structure and morphology of the cranial nerves and lateral sense 

 organs of Fishc'^, with special reference t"^ the genu.-; Gadus, Trans. Linncan Socleti/ nf 

 London, 2nd series, Zoology, Vol. vii. , London, 1898. 



