Bull. U. S. F. C. 1897. (To face page 426.) 
Plate XIII. 
• JJ 
m 
« 
i 
3 
m 
# > 
5 
6 
^ 8 
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V 
J 0 '' 
9 
10 
II IS » (3 
ROUND AND 
ELONGATED PEARLS. 
PEARLS PRESENTING THE ASPECT OF HAVING BEEN TURNED IN A LATHE, I. E., WITH ONE OR MORE 
REGULAR RIDGES OR FURROWS RUNNING COMPLETELY AROUND THEM. 
In form these pearls may be either round, pear-shaped, club-shaped, top-shaped, or flattened like a quoit. Some of them are plainly cases of coalescence 
(two left-hand figures of middle row and two central figures of bottom row; compare, also, Plate XIV, Group A, fig. 6); others may be due to a turning 
and rolling process which' is believed by some to be constantly practiced by the animal in the case of "free " pearls. 
