WILLIAMS : MIGRATION OF EYE IN PSEUDOPLEUllONECTES. 23 



su'orb. dx.), as but now described for the specimen that had lost the left 

 eye, is the backward extension of a plate of cartilage which connects the 

 right ect-ethnioid with the naedian mes-ethmoid arch. This flattened 

 anterior portion of the right supraorbital cartilage corresponds to the 

 tegmen cranii of the right side of the head in the salmon. The median 

 mes-ethmoid arch is, at its anterior end, fused to this plate or partial 



irb. su''orb. dx. trb- 



ec'eth, s. 



for. olj. s. 



cri. orb. a. 

 pt-pi:l. a. 



bn-hy. 



vrl. mk. 



Fig. C. 



From photograph of wax model of the fackil cartilages of a large specimen of 

 P. americnnus intermediate between the stages shown in Fig. B. and 

 Fig. />. Viewed from a point nearly in front, only a little to the right of 

 the sagittal and a little above the horizontal plane. X 45. 



For meaning of lettering, see Abbreviations under Explanation of Plates. 



tegmen, but from the short region of fusion backward for some distance 

 the two cartilages are merely crowded closely together, a distinct line 

 of perichondria! connective tissue being found between them. The car- 

 tilages then diverge, as may be seen in Figure C, and the median mass 

 continues backward as the fused trabeculae cranii, while the higher, lateral 

 portion, the right supraorbital bar (trb. su'orb. dx., Figs. C and C), 

 passes upward ami backward to the ear capsule. 



