MR. R. OWEN ON THE ANATOMY OF THE BRACHIOPODA. 161 
Fig. 10. A small portion of one of the arms, magnified. 
11. A small portion of the edge of the mantle, highly magnified. 
a. The branchial cilia. 
B. The marginal fringe. 
y. The marginal canal. 
8. The branchial artery. 
e. The branchial vein. 
Z. Ova. 
12. The alimentary canal, as seen from above or behind, and a portion of the 
liver of Terebratula psittacea, Brug., magnified. 
a, The mouth. 
B. The esophagus. 
y. The stomach, with the parietes imperfect where the liver has been re- 
moved: it is turned towards the left side, to show 
8. The intestine. 
e. The anus. 
z. A portion of the liver. 
13. A few of the hepatic follicles, highly magnified, showing the vascular net- 
work upon their parietes formed by the hepatic vessels. 
14. Terebratula psittacea, with the greater part of the imperforate valve removed 
to show the soft parts. 
14*. Terebratula psittacea, with the perforate valve and lobe of the mantle re- 
moved to show the arms, one of which has been artificially unfolded. 
15. Terebratula Sowerbii, King, natural size: the greater part of the perforate 
valve has been removed to show the ova accompanying and obscuring the 
branchial vessels, seen through the mantle. 
16. The separated valves of Terebratula Sowerbii: in the imperforate valve the 
arms, and one lobe of the mantle have been removed, to show the cal- 
careous loop, visceral mass, muscles and ova, surrounding the vessels of 
the opposite mantle-lobes. 
The following letters indicate the same parts in each figure. 
a. The mantle-lobe of the imperforate valve. 
b. The mesial fissure, corresponding to the mesial process of that valve. 
c. The mantle-lobe of the perforate valve. 
d. d. The fringed margins of the mantle. 
e. The tubular prolongation accompanying the pedicle. 
f.f. The anterior pair of muscles arising from the imperforate valve. 
g.g. The posterior pair of muscles arising from the imperforate valve. 
g'.g'. Fig. 16. The insertion of these muscles into the pedicle. 
h. h. The anterior pair of muscles arising from the perforate valve. 
