No. 440.] 



STLl'IES OF GASTROPODA. 



5 35 



volutions (including the protoconch) were 14, 13, and 12 

 respectively. Out of thirteen specimens, the average for the 

 6th and 7th volutions were 12 and 11 periods respectively, 

 while 13 for the 5th volution is not uncommon. In old age or 

 pathologic individuals the number of periods in the last portion 

 of the final whorl becomes much greater as the periodic additions 

 to the shell between resting stages are much shorter. Thus it 

 appears that in normal progressive types the period increases in 

 length as the shell increases in size, and at a rate more rapid than 

 the increase of the shell. The number of spines on each suc- 

 ceeding whorl is therefore fewer. Judged by this standard, 

 F. clkeam must be considered more accelerated than F. cariaim. 

 In F. cliccans the average periods for the 5th, 6th, and 7th 

 volutions are more nearly 12, 9, and 6 respectively. Finally, 

 in F. candelabrum we have extreme acceleration in this respect, 

 as the final whorl is provided with only three periods and spines. 



Relatives of Fulgur and Sycotypus. 



Among the near relatives of Fulgur and Sycotypus in the 

 modern fauna we may mention Fasciolaria and Buccinum. A 



