56 THE PHYSIOLOGY OF THE COMMON CRAYFISH. 
a broad plate, hairy on its inner surface, which enters 
into the lateral wall of the cardiac chamber. There are 
various other smaller skeletal parts, but the most im- 
Fig. 10.—Astacus luciatilis.—Longitudinal section of the stomach (x 4), 
c, cardiac ossicle; cw, caecum ; ¢..v, cardio-pyloric valve; cs, cushion- 
shaped surface ; jg, hind-gut ; ip, aperture of right bile duct ; lp, 
lateral pouch ; 7, lateral teeth ; mg, mid-gut ; mt, median tooth ; as, 
cesophagus ; p, pyloric ossicle ; pe, pterocardiac ossicles ; pp, prepy- 
loric ossicle ; we, urocardiac process ; v!, median pyloric valve; v2, 
lateral pyloric valve; x, position of gastrolith; zc, zygocardiac ossicle. 
portant are those which have been described; and these, 
from what has been said, will be seen to form a sort of 
hexagonal frame, with more or less flexible joints at the 
angles, and having the anterior and the posterior sides 
