BRACHIOPODA. 
117 
From their point of union a single process is extended backward at an 
abrupt angle and with a very gentle downward curve, terminating just in front 
Two views of the.loop of Eumetria Verneuiliana, Hall. (C.) 
of the apices of the primary lamellae and above the bases of the spiral cones; 
its extremity is broadened and bifurcated, these secondary processes, however, 
extending but a very short distance. The posterior edges of the lateral branches 
of the loop and of the primary lamellae may be finely fimbriated. 
There is usually no trace of a median septum in this valve, but occasionally 
an obscure ridge is preserved. No muscular markings have been observed. 
The external surface is covered with numerous fine radiating striae, which 
are rarely crossed by concentric lines. Shell-substance abundantly punctate. 
Type, Retzia vera, Hall. Kaskaskia limestone. 
Observations. The term Eumetria was proposed as a designation for shells 
which were believed to differ in the structure of the deltidium from forms at 
that time regarded as typical of the genera Retzia and Rhynchospira. In treat¬ 
ing of the genus Rhynchospira it has been shown that the coalescence of the 
deltidial plates may occur in the early forms of that genus, as it does also in 
Retzia and Nucleospira, but nowhere does it become so well marked and not¬ 
able a character as in the group of fossils under discussion. It was also shown 
in the original description of the genus Eumetria, that the umbonal cavity of 
