24fi 



spines and epural and hypuial bones are 

 beginning to ossify from without inwards. 

 The fig. should be compared with fig. 14. It 

 shows that the urostyle has not yet fused 

 with the third hypural, and that the caudal 

 fin of the young Plaice is of the ordinary 

 homocercal type. 

 Fig. 16. Longitudinal section through a fin ray and 

 axonost of the dorsal fin of a medium sized 

 adult Plaice, i.e., the section passing longi- 

 tudinally through the fin ray and transversely 

 to the long axis of the fish. Leitz 3, ocular 

 2. The figure shows the two pieces forming 

 one fin ray, and their relations and connec- 

 tions with the baseost and axonost. The 

 section does not pass through the plane of 

 the elevator and depressor muscles of the fin 

 ray, or the longitudinal vertical ligament of 

 the axonosts. 



Plate IY. 



Fiff. 17. Moist dissection from the eveless or left side of 

 the anterior part of the dorsal fin and first 

 three trunk vertebrae of a 52cm. Plaice. 

 Natural size. The outline of the skull is 

 introduced to show its ventral inclination 

 and its relation to the first eight-ten 

 axonosts of the dorsal fin. (Cp. table in 

 text.) The first three vertebrae also have a 

 downward inclination. 



Fig. 18. Moist lateral dissection from the eyeless side of 

 the last four trunk and first three caudal 

 vertebrae, and of the anterior extremity of 

 the anal fin and its supports of a 52cm. Plaice. 



