PLATE 15 



EXPLANATION OF FIGURES 



Cross-sections of metamorphic stage III. X 28 



41 Level corresponding to larva, figure 12, and adult, figure 26, showing the 

 rapidly ossifying os thyreoideum, the M. thoracicohyoideus degenerating and 

 M. abdominohyoideus developing, and the M. ceratohyoideus internus beginning 

 to form the spiral. 



42 Level corresponding to larva, figure 14, and metamorphic stage II, fig- 

 ure 36, showing the further development of the adult epibranchial and spiral 

 muscle, and the almost complete degeneration of the larval first and second 

 epibranchials. 



43 Level corresponding to larva, figure 15, showing the M. sternohyoideus 

 completely separated from the thoracicohyoideus and the adult epibranchial and 

 spiral muscle formed, the posterior ends of the larval epibranchials still present. 



580 



