MAZATLAN UNIVALVES 469 
596. OLIVELLA TERGINA, Ducl. 
Oliva tergina, Ducl. Mon. Oliv. p.7, pl. 2, £.18,14.—Mke.in 
Zeit. f. Mal. 1847, p. 183, no. 24.:—do. 1851, p. 25, no. 107.— _, 
Rve. Conch. Ic. pl. 26, f. 80. 
Olivella tergina, H. § A. Ad. Gen. i. 146. 
This appears to be the common Olive of the Mazatlan fauna, 
as O. volutella is of that of Panama. The latter was abundant 
in the S. W. Mexican collection ; but (as far as authentic infor- 
mation is concerned) is entirely unknown in the Gulf district. 
The great bulk of the specimens are sufliciently constant in 
characters to be easily recognized, having grey marking on a 
light ground; but these often assume a fawn or orange tint, 
or on the other hand arich purplish brown, and are sometimes 
absent altogether. The dried animals, which were abundant 
and easily softened, gave no token of opereula. The West 
Indian analogue is O. conoidalis. An acuminated specimen 
measures long. °72, long. spir. °33, lat. °28, div. 50°. 
A broad sp. me eo, sp 38 aa diiiars Yom 9 Ft \) 2 
The difference of divergence is in the later, not the earlier 
whirls. ' 
Hab.—Conchagua; on sand banks; Cuming.—Mazatlan ; in 
extreme profusion ; L’pool § Havre Coll. 
Tablet 2170 contains 8 sp. uniform, light passing into dark 
orange.—2171, 7 sp. do. with slight markings.—2172, 15 sp. 
light passing into dark flesh colour, nearly uniform. — 2173, 
15 do. with slight markings. —2174, 8 do. markings richly 
developed.—2175, 15 sp. darker shade, markings faint.—2176, 
15 do. markings developed.—2177, 15 do. orange passing into 
srey.—2178, 15 do. light to dark.—2179, 8 sp. light to dark 
brown.—2180, 15 sp. changing to rich, nearly uniform, purple 
brown, with dark spire. 
Normal state. Tablet 2481 contains 8 sp. light shade.— 
2182, 15 do. ordinary state.—2183, 15 sp. zigzag pattern deve- 
loped.—2184, 15 sp. spire dark. 
597. OLIVELLA anazoRa, Ducl. 
Oliva anazora, Ducl. Mon. Oliv. pl. 5, f. 3, 4—Mke. in Zeit. 
JF. Mal. 1851, p. 25, no. 106.— Rve. Conch. Ic. pl. 25, f. 74. 
Olivella anazora, H. & A. Ad. Gen. i. 145. 
Intermediate in character between the elevated, light variety 
of O. tergina, and O. petiolita. Known from the former by 
Feb. 1857. rr 
