246 
spines and epural and hypural 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, z.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. 
Prate ly. 
Fig. 17. Moist dissection from the eyeless or left side of 
the anterior part of the dorsal fin and first 
three trunk vertebre 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 vertebra also have a 
downward inclination. 
Fig. 18. Moist lateral dissection from the eyeless side of 
the last four trunk and first three caudal 
vertebree, and of the anterior extremity of 
the anal fin and its supports of a 52em. Plaice. 
