REVIEW OF THE PARROTFISHES 5 



being considered rudimentary if it arises in the usual position for the 

 haemal spine but does not reach the next posterior vertebra. Some 

 individuals had rudimentary haemal spines on the eleventh vertebra, 

 but a rudimentary haemal spine was found on the twelfth vertebra 

 only on Chlorurus gibbus. If a rudimentary spine occurred on the 

 tenth or on the eleventh or twelfth vertebra the next posterior vertebra 

 always had a haemal spine that extended to opposite or beyond the 

 tips of the first few anal pterygiophores. All vertebrae with rudi- 

 mentary haemal spines were counted as abdominal vertebrae. 



The occurrence of rudiments of haemal spines suggests that the 

 haemal spines in the subfamily Scarinae may be in the evolutionary 

 process of becoming reduced in development or lost, thus increasing 

 the number of abdominal vertebrae from 9 in the Sparasomatinae 

 to 10 to 12 in the Scarinae. 



Table 1. — Number of vertebrae recorded from radiographs of genera and species of 



Scaridae 



See footnotes at end of table. 



