i2 MAZATLAN BIVALVES 
into atube. The epidermis is extremely thin, but important 
to preserve the shell, which soon becomes of a calcined appear- 
ance without it. The radiating striz become obsolete in the old 
shells, but not so much so as in Ch. amathusia. The smallest 
valve measures ‘03 in length: the largest specimen, Jong. 3°5, 
lat. 3°56, alt. (without spines) 2°3. 
Hab.—Payta, Peru, Fontaine, D’Orbigny.—Panama, rare, C. B. 
Adams.—San Blas, Jay.—Mazatlan; Lieut. Green, (Gould 
ms.) ; extremely abundant; L’pool & Havre Coll. 
Tablet 319 contains 3 very young valves.—320, 4 young 
specimens, form somewhat rounded.—321, 3 do. adolescent.— 
322, 3 do. adult.—323, 3 young, slightly produced.—324, 3 do. 
adolescent.—325, 2 do. adult, ribs close.—326, 3 do. young, 
more produced.—327, 2 do. adult.—328, 4 young, rather flat- 
tened, with distant laminz.—329, 3 do. adolescent.—330, 2 do. 
adult.—331, 5 young specimens set to shew the ventral margin 
in different stages of growth.—332, 4 do. adolescent.—333, 4 do. 
adult.—334, 2 sp. shewing the nearest approach to Ch.amathusia, 
and unnatural longitudinal grooves.—335, 1 sp., ribs not foli- 
ated ventrally.—336, 2 do., ribs flattened.—337, 1 do., strongly 
foliaceous.—338, 1 do., foliations semispinous.—339, 1 sp. de- 
formed growth.—340, 3 do. with irregular ribs. In all 59 
specimens. 
102. Venus (CHIONE) AMATHUSIA, Phil. 
Venus amathusia, Phil. Abbild. p. 129, pl. 2, f. 4.—C. B. Ad. 
Pan. Shells, p. 269, no. 435.—Sow. Thes. Conch. p. 709, 
pl. 154, f. 26, 27. 
Chione gnidia, var. Desh. B. M. Cat. Ven. p. 133, no. 41. 
+ Chione amathusia, Desh. do. p. 132, no. 39. 
P= Venus cancellata, Menke in Zeit Ff. Mal. 1847, p. 191, no. 
58, (non Lam.) 
P= Venus succincta, Val. in Humb. Rec. d’ Obs. vol. ii. 
I follow Hank Sow. and ?C. B. Ad. in regarding this as 
Philippi’s species. It agrees exactly with the description ; not 
with the figure. I have however avery worn young stumpy 
specimen from S. W. Mexico, which is sufficiently like the 
figure, especially when it is remembered that figures are not 
always like the shell. I cannot say that I should have known 
it even from Sow.’s figure, which is much better. Desh. re- 
gards Phil.’s species as distinct, and (with Dr. Gray) considers 
this a variety of Ch. gnidia. What changes the creatures make 
