b MAZATLAN BIVALVES 



the inner one turned backward. In the adult, this row ceases. 

 The very young shell has none ? while in D. Teneris they ap- 

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

 rather straight and very long; one measured long. 1*88, 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 apex. Epidermis extremely thin : spines 

 channeled. The spine of the smallest well marked specimen 

 measures "41 ; the shell itself long. *49, lat. '59, alt. '31. 

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

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



Hob. Salango, in sandy mud, 9 fm. ; Tumbez (Peru) soft mud, 



5 fm. : Cuming. San Bias (Gulf of California), sandy mud, 



7 fm., Col. Cuming. Payta, (Peru,) IfOrbigny. Mazatlan; 



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



# Havre 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 contains 9 very young specimens, rounder form, 

 with rather coarser striae. 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 P VULNEEATA, Srod. 



Cytherea vulnerata, Proc. Zool. Soc. 1835, p. 46. Hani Descr. 



Cat. p. W5.Catlow. Cat. p. 40, no. 116. Sow. Thes. Conch. 



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

 Dione vulnerata, Desk. B. M. Cat. Yen. p. 60, no. 15. 



Tablet 313 contains 2 minute opposite valves which may 

 belong to this species. 

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



2 valves off Spondylus ; L'pool Col. 



