Fig. 171b.—Section through the Fig. 171c.—The oyster-drill. 
oyster along the line o of Fig. 1%1c (Natural size.) 
enlarged twice). a’, a’’, dorsaland 
ventral branches of the anterior 
aorta in section; br, artery to gills; 
c, connective tissue; g, gills in sec- 
tion; g’, internal cavities of the gills; 
ge, egg-gland; i, 7, cross-sections of 
the intestinal tube; 2, liver; mt, 
mantle; sb, suprabranchial or water 
spaces above the gills; st, stomach; 
ve, vena cora.—After Ryder. 
Fig. 171a.—Oyster. Gen, gland in which the eggs are formed; ov, oviduct, 
from which the eggs ‘are discharged; mus, adductor muscle; H, heart; mt, 
mantle; P, palp; G, gills.—After Ryder. 
ita ‘ aS [To face page 232.]: 
