MAZATLAN BIVALVES 67 
The largest specimen measures long. 1°97, lat. 2°38, alt. 1°06. 
A transverse specimen _,, ait whites tis eaCdds yeep 
Hab.—Found abundantly at San Blas, Lieut. Belcher, (Beech. 
Voy.)—Panama, Cwming (teste Sow.: non C. B. Ad.).— 
Mazatlan ; abundant ; L’pool & Havre Col. 
Tablet 284 contains a minute valve, probably belonging to 
this species, measuring ‘06 across. 
Tablet 285 contains 7 specimens, normal type.—286, 5 do. 
dark coloured, transverse.—287, 3 do., brownish tinge.—288, 
3 do. lamine slightly raised; the largest was attacked by a 
gasteropod, who left his hole unfinished.—289, 3 do. pinker 
shade.—290, 3 do. more produced ventrally.—291, 3 do. most 
produced.—292, 3 do. coarse ribs.—293, 3 do. very pale. 
95. Dione Lupinaria, Less. 
Cytherea lupinaria, Less. Cent. Zool. p. 196, pl. 64.—Sow. Thes. 
Conch, p. 632, f. 111. 
Venus lupanaria, B. MZ. Cat. D’ Orb. Moll. p. 67, no. 593. 
Chione lupanaria, Gray Anal. viii. 306. 
Dione lupanaria, Desh. B. M. Cat. Ven. p. 76, no. 68. 
Cytherea Dione, var. Brod. Proc. Zool. Soc. 1845, p. 45-6.— 
Gray in Griff. Cuv. An. King. pl. 19, f. 1.—Rve. Conch. Syst. 
moo: ple Wily fds 
Cytherea semilamellosa, Gawd. in Deless. Ree. pl. 19, f. 2.— 
Chénu. Conch. Lil. pl. 9, £. 9. 
This shell is sometimes shaped like its well known W. Indian 
analogue, V. Dione, Zin. (Dione Veneris, Desh.): but is almost 
always larger and more transverse. It is known at once by 
the concentric ridges, which are never sharp and raised as in 
D. Veneris, but either rounded or sub-obsolete on the ventral 
part. Many of them (generally every other, or 1 out of 3) 
become obsolete before reaching the anterior part ; the remain- 
der become sharply lamellar, gradually fading off to the lunule, 
not suddenly ending there asin D. Veneris. The posterior 
part has two angular swellings, one in the line of the inner 
spines, the other just beyond the ligament. The inner area, 
lunule and bases of spines are almost always purple even in 
the pale variety. There are all shades of colour from white to 
rich puse or purple. The spines appear very irregularly, 
sometimes two or more growing together, sometimes leaving a 
large space without. The young shell has always two rows, 
