64 MAZATLAN BIVALVES 
Tablet 267 contains 2 minute valves, the smallest °03, across, 
which may belong to this species. 
Tablet 268 contains 2 young specimens.—269, 2 sp. very 
large.—270, a distorted sp. with one valve overlapping.—271, 
another distorted sp. with a large anterior gape. 
93. Dionr cH1onmuA, Menke.* 
Cytherea chionea, Menke in Zeit. f. Mal. 1847, p. 190, no. 57. 
Cytherea squalida, Sow. Proce. Zool. Soc. 1835, p. 23.—Hanl. 
Descr. Cat. p. 104: Wood’s Suppl. pl. 13, f. 40.—Sow. Thes. 
Conch. p. 629, pl. 131, f. 87-89.—C. B. Ad. Pan. Shells, 
p. 273, no. 447. 
Chione squalida, Gray Cat. Cyth. Anal. 1838, viii. 306. 
Venus squalida, B. M. Cat. D Orb. Moll. p. 68, no. 609. 
Dione squalida, Desh. B. M. Cat. Ven. p. 58, no. 6. 
+ Cytherea biradiata, Gray, Zool. Beech. Voy. 1839, p. 151, 
pl. 43, f. 5.—Svebold. in Wiegm. Arch. 
+ Cytherea chione, pars, Sow. Thes. Conch. p. 629, no. 59. 
?=Cytherea elegans, Koch. in Phil. Abbild. Conch. Cyth. 184A. 
p. 2 (150) pl. 1, f. 4. 
For a full description of the main features of this shell, v. 
Cytherea chione, Forbes & Hanl. Br. Moll. i. 396—8, which 
applies in most of the minute particulars, even in that which 
is said to separate it, the 3 short ray-like colourless markings 
of which the central is the shortest, and the others margin the 
commencement of the lunule and the ligamental area. It is 
necsssary however to state, for the benefit of those who think 
* The learned have hardly behaved well to this exquisitely:beautiful species. It 
was first described from some Peruvian shells of a ‘‘very dull and dirty aspect,” by 
Sow., under the name (very inappropriate to the species generally) of C. squalida. 
He confesses however that one of the varieties is ‘‘ rather agreeably ornamented 
with concentric purple bands.” The Mazatlan shells were next described by 
Gray, in the Zool. Beech. Voy., as C. biradiata, a name applicable again only to 
a portion of the species. The East Indian shells were next named by Koch and 
described by Phil. in 1844s C. elegans. Then Sow. jun. in 1851 gives in quo- 
tations (as though from the P. Z.S.) a fresh description of C. squalida, with 
only 6 of the original words, adding with singular inappropriateness ‘‘rubente- 
albicante radiata ; costellis numerosis, concentricis, obtusis, econcinnis, confertis.”” 
He also tells us (an error which C. B. Ad. very politely exposes) that the species 
was first named from Philippine specimens brought by Mr. Cuming; and also that 
the name OC. biradiata in Beechey’s voyage was given to the Philippine shells. 
Not content with these errors, he also informs us that Mr. Cumings’s Mazatlan 
specimens belong to the Europzan C, chione.—Last of all Menke gives the name 
C. chionza to the Mazatlan species; and though he only describes from a single 
specimen, it fortunately happens that both name and description are sufficiently 
comprehensive. As the prior names only apply to portions of the species, the 
ordinary rules of priority are disregarded in order to retain an expressive name 
which includes the whole species. 
