CLASS BRACHIOPODA. 133 
THECIDEA, Defr., 
This support seems to have been incorporated with the small 
valve. (Thecidia Mediterranea, Risso.) 
ORBICULA, Cuv. 
The orbiculz have two unequal valves, one of which, that 
is round and conical, when viewed by itself, resembles the 
shell of a patella; the other is flat, and fixed to a rock. The 
arms of the animal (Criopus, Poli), are ciliated and spirally 
recurved, like those of the lingule. 
The seas of Europe produce a small species, Patella ano- 
mala, Miill. Zool. Dan. V. 26 ; Anomia turbinata, Poli, XXX. 
15; Brett., Sowerb., Lin. Trans. XIII. pl. xxvi. f. 1. 
The Discina, Lam., are orbicule, the inferior valve of 
which is marked by a fissure. The 
CRANIA, Brug., 
Should be approximated to the orbicule. The arms of the 
animal are also ciliated, but the shells have internally deep 
and round muscular impressions, that have caused it to be 
compared to the figure of a skull. 
One of them inhabits the European seas, Anomia cranio- 
laris, L., or Crania personata, Bret., Sowerb., Lin. Trans. 
XIII. pl. xxv. f. 3. Several are fossil, such as the Cran. 
antiqua, and the others, of which M. Heeninghaus has given 
an excellent monograph. 
