464 TRANSACTIONS LIVERPOOL 
NV. ot. = Otocyst nerve. 
N. p. = Pedal nerves. 
N. pa. = Ant. pallial nerve. 
N. pall. = Visceral pallial nerve. 
N. pp. = Post. pallial nerve. 
0. = Ova. 
O’ = Young ovum. 
Op. F. = Ophthal. pallial fold. 
Op. m. = Kye stalk muscles. 
Op. n. = Optic nerve. 
Op. n. 7. = Inner branch ditto. 
Op. n. 0. = Outer branch ditto. 
Ot. = Otocyst. 
= Periostracum. 
i= Byssal groove. 
gr. = Periostracal groove. 
M.r. = Radial pall. muscles. 
= Periostracal glands. 
= Pericardium. 
= Pigment cells. 
= Rods of retina. 
BIOLOGICAL SOCIETY. 
fo. m. = Intrinsic muscles, renal org. 
Ro. rp. = Reno-reprod. apert. 
Ro. v. = Renal veins. 
S. = Spermatozoa. 
S. D. = Dors. venous sinus. 
S.m.t. = Basement membrane. 
S.m.o. = Sieve membrane. 
S. V.r. = R. vent. venous sinus 
Sols — Scleroticas 
Sep. = Septum. 
Sh. a. = Auricula of shell. 
Sh. ’. = Shell fold, mantle. 
Sh. m. = Calcar. layer of add. impress. 
Sh. p. = Artic. surf. of shell. 
T. = Tapetum. 
Tn. = Tentacle. 
Tn. v. = Velar tentacle. 
Tu. m. = Tunica muscularis. 
Tu. p. = Tunica propria. 
V. = Velum. 
V. a.= Adductor veins. 
= Rod-cells ditto. 
. = Nuclei, rod cells. 
P. = Pseudo-rod cells. 
V h. = Hepatic vein. 
V. M. = Radial velar muscles. 
V. M. a. = Attach. of velar muse. 
SARPREPERUES 
> Ccy| = 
9, = Renal organ. V. M. c. = Concent. velar muse. 
Ro. = Gland. epith. ditto. V. p. = Pedal vein. 
Ro. c’. = j)itto, with coneretions, V. pall. = Pallial vein. 
Ro. con. = Connect. tissue, renal org. V. v. = Visceral veins. 
Ro. ep. = Epithel., renal org. Ven. = Ventricle. 
Puate I. 
Fig. A. P. opercularis, right valve, showing byssal 
notch. Natural size. 
Fig. B. P. opercularis, left valve. Natural size. 
fo) 
Fig. C. P. maaimus, exterior R. valve (young). x 2. 
Fig. D. P. maximus, exterior L. valve (young). x 2 
fig. E. PP. maximus, interior of R. valve, showme 
adductor impression and pallial line (slightly 
darkened}, also hgament and ridges of hinge 
colt 
° 
area. x 
Fic. F. P. masimus, interior of L. valve; pigmented 
specimen showing muscular impressions. x 3. 
