THE 
AMERICAN NATURALIST. 


Vor. XXXIX. October, 1905. No. 466. 

A PECULIAR VARIATION OF TEREBRATALIA 
TRANSVERSA SOWERBY. 
IH. W. SHIMER. 
Tuis specimen (Figs. 2-5) of this very variable species differs 
from tbe type as figured by Davidson (Fig. ı) in its more 
elongate form, thicker valves, obscurity of plications, and less 
development of the mesial sinus in the brachial valve.! Aside 
from its normal variation the specimen is remarkable for its 
extremely rugose surface due to the great inequality in the 
development of growth lines.and also for the greatly abraded 
umbo of the pedicle valve. This abrasion is so great that it 
brings to view the unfilled cavity behind the buttress support- 
ing the teeth which shows as a rounded hole, through which a 
- bristle can be passed, on each side of the pedicle opening. 
Dall, after an examination of this specimen, wrote us that it 
is *an unusually worn and deformed specimen which has been 
crowded by its fellows so as to grow out of shape and worn by 
rocking on its pedicle until at least one quarter of an inch of 
shell has been removed." In reference to the two holes above 
1 For other figures and variations of this species see “ A Monograph on Recent 
Brachiopoda ” by Davidson, Trans. Linn. Soc. London, ser. 2, vol. 4, and Amer. 
Journ. Conch., vol. 6, pl. 6. 
691 
