164 MR. R. OWEN ON THE ANATOMY OF THE BRACHIOPODA, 
valve, or the one which corresponds to the imperforate valve of Orbicula, 
and to the perforate valve of Terebratula. 
k. k. 
Lt. 
m. M. 
. The shell-secreting margin of the mantle. 
. The cavity containing the roots of the cilia. 
. The same laid open. 
. The branchia. 
. The branchial vein. 
. The interbranchial space of the mantle, which is also vascular. 
. The anterior muscles, attached at one extremity only to the shell. 
. The anterior pair of shell-muscles analogous to the anterior shell- 
muscles of Orbicula. 
. The third pair of muscles analogous to the decussating muscles of 
the viscera in Orbicula. 
. The posterior shell-muscle. 
The liver seen through the mantle. 
The straight portion of intestine. 
The ovaries. 
Fig. 16. A magnified view of the respiratory organs of one of the mantle-lobes. 
a, b, b', c, d, e, signify the same parts as in the preceding figure. 
17. Lingula Semen, Brod. 
