68 MAZATLAN BIVALVES 



the inner one tiirned backward- In the adult, this row ceases. 

 The verj" yovmg shell has none ; while in D. Veneris they ap- 

 pear much earher. The spines in the large row are generally 

 rather straight and very long; one measured long. 1'8S, and 

 others must have been longer when perfect. The concentric 

 ridges are not always parallel with the margin of the shell, and 

 often bifurcate very irregularly. I have examined carefully 

 nearly 4,000 specimens, almost all of which had fallen victims 

 to the voracious appetites of gasteropods, who drill their holes 

 generally near the apes. Epidermis extremely thin : spines 

 channeled. The spine of the smallest weU marked specimen 

 measures '41; the sheU itself Zo«(/. '49, lat. 'o9, alt. "31. 

 The largest (without spines) „ 2'26, „2'77, „ 1"5. 

 The most transverse ,, 1'53, „ 2'06, „ 1'03. 



Hab. — Salango, in sandy mud, 9 fm. ; Timibez (Peru) soft mud, 



5fm. : Ciimi)ig.— San Bias (Culf of California), sandy mud, 



7 fm., Col. Cuming. — Paj-ta, (Peru,) D'Orhigtry. — Mazatlan; 



Col. Jewett, (Gould ms.) — Do ; extremely abundant, L'pool 



^* Savre Coll. 



Tablet 294 contains 2 minute valves, (the smallest '025 

 across,) which probably belong to this species, though they 

 shew no trace of spines. 



Tablet 295 contams 9 very young specimens, roimder form, 

 with rather coarser stria?. — 296, 6 do. rather older. — 297, 3 do. 

 adolescent. — 298, 2 do. very large. — 299, 9 very young, trans- 

 verse form. — 300, 8 do. rather older. — 301, 6 do. adolescent. — 

 302, 3 do. adult. — 303, 5 young, pale var. — 304, 3 do. adult. — 305, 

 4 sp. with extra spines. — 306, 1 large do. shewing epidermis. — 

 307, 3 young, spines forming at margin. — 308, 3 do. spines 

 strangely curved. — 309, 2 do. small spine growing by and in 

 broken large one. — 310, 1 adult, with spurs on bottom of 

 spines. — 311, 1 do. two spines growing together. — 312, 1 do. 

 very crowded spines at margin. In all, 72 specimens. 



96. DiONE ? VULNEKATA, Brod. 



Cytherca viJnerata, Proc. Zool. Soc. 1835, p. 46. — Sanl. Descr. 



Cat. p. IQ^.—Catlow. Cat. p. 40, no. 116.— &«•. Thes. Conch. 



p. 632, pi. 131, f. 95, 96. 

 Dione vulnerata, Besh. JB. M. Cat. Ten. p. 60, no. 15. 



Tablet 313 contains 2 minute opposite valves which may 

 belong to this species. 

 Hah. — Eeal Llejos, in sandy mud, 6 fm. Cuming. — ? Mazatlan ; 



2 valves off Spondylus ; L'pool Col. 



