550 THE AMERICAN NATURALIST. (VoL. XXXIX. 
by others in the Cephalopoda, Pelecypoda, Gastropoda, and 
Brachiopoda and they are seen in still other groups. 
Uncoiling.— Cristellaria siddalliana Brady (Fig. 21) shows 
an excellent case of uncoiling not carried to an extreme. The 

2I 
FIG. 21.— Cristellaria siddalliana Brady, showing uncoiling in last few chambers. 
FIG. 22.— Trochammina lituiformis Brady, showing uncoiling carried to an extreme. 
early chambers are close-coiled and this feature continues until 
the last few chambers. Here there is a distinct change and 
an uncoiled form is produced as shown in the figure. This 
uncoiling is only seen in well advanced specimens that show old 
age characters. Other examples of uncoiling in Cristellaria 
have already been given (Figs. 11, 12). Although outside of 
this family, Trochammina lituiformis Brady is figured (Fig. 22) 
to show the character of uncoiling carried to an extreme. The 
early chambers make a little more than a single volution, while 
the succeeding growth is uncoiled. In old age specimens, this 
character may be carried to a greater extent than is shown in 
Fig. 22. In this species in contrast to the preceding, the 
majority of the chambers. form the uncoiled portion of the shell. 
Such examples are exactly comparable to Baculites or Lituites 
