MAZATLAN BIVALVES 67 



The largest specimen measures Z0W5'. 1" 97, lat.2'd8, aii.1'06. 

 A transverse specimen „ „ 1'72, „ 2'11, „ "87. 



ITab. — Found abundantly at San Bias, Lieut. Belcher, (Beecli. 

 Voy.) — Panama, Cuming (teste Sow. : non C. B. Ad.). — 

 Mazatlan ; abundant ; L'pool Sf Havre Col. 



Tablet 284 contains a minute valve, probably belonging to 

 tliis species, measm*ing "06 across. 



Tablet 285 contains 7 specimens, normal type. — 286, 5 do. 

 dark coloured, transverse. — 287, 3 do., brownish tinge. — 288, 

 3 do. laminae slightly raised ; the largest was attacked by a 

 gasteropod, who left his hole imfiuished. — 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 LUPiNAEiA, Less. 



Cytherea lupinaria, Less. Cent. Zool. p. 196, pi. Q4s.—Sow. TJies. 



Conch, p. 632, f. 111. 

 Venus lupanaria, B. M. Cat. IfOrh. Moll. p. 67, no. 593. 

 Chione lupanaria, Gray Anal. viii. 306. 

 Dione lupanaria, Besh. B. M. Cat. Ven. p. 76, no. 68. 

 Cytherea Dione, var.. Brod. Proc. Zool. Sac. 1845, p. 45-6.— 



Gray in Grijf. Cuv. An. King. pi. 19, f. \.—Bve. Conch. Syst. 



i. 95. pi. 71, f. 1. 

 Cytherea semilamellosa, Gaud, in Beless. Bee. pi. 19, f. 2. — 



Chenu. Conch. III. pi. 9, f. 9. 



This shell is sometunes shaped like its well known W. Indian 

 analogue, V. Dione, Lin. (Dione Veneris, Desk.) : 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 as in D. Veneris. The posterior 

 part has two angular swellings, one in the line of the inner 

 spines, the other just beyond the Hgament. The inner area, 

 lunule and bases of spiues 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 gi-owing together, sometimes leaving a 

 large space without. The young shell has always two rows, 



