158 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
seaweed. It arrived with the umbonal region of one valve 
broken, the fractured portion standing at right angles to the 
vertical axis. Jeffreys reports the same characteristic in an 
EngUsh species of Thracia. He says, "The power of tension 
continually exercised by the strong and elastic cartilage exceeds 
Fig. 16. — Thracia conradi Couthouy. 
that of the shell and the latter being the weaker body gives way 
and is split in the conflict. " 
In most of the earlier descriptions the syphonal openings of 
Thracia are described as fringed and figures of the English species, 
Thracia phaseolina and distorta in Forbes and Hanley, represent 
the syphonal openings as densely fringed. The figures are 
entirely wrong as the descriptions from Clark indicate. The 
specimen of Thracia conradi remained in a vessel of sea-water for 
three days without showing signs of Ufe. At one time the 
