468 MAZATLAN UNIVALVES 



Voluta tenebrosa, (Mawe) Wood, Ind. Test. Suppl. pi. 4, f. 38. 

 Olivella undatella, H. fy A. Ad. Gen. i. 146. 

 Comp. Oliva zonalis, Wee. in Zeit.f. Mai. 1847, p. 183, no. 25 ; 

 non Lam. 



This species varies, as usual, in the elevation of spire and 

 the comparative breadth : but its principal changes are in 

 colouring ; passing from pure white to rich purple or more 

 usually with zigzag or undulating markings, pink on a white 

 ground, or, (normally) with various shades of dark olive. The 

 spiral band occupies more or less of the back, at a greater or 

 less angle. Although the animal remained in many of the 

 specimens, sufficiently fresh to swell out in water, no trace 

 of operculum was found. The largest of the specimens 

 measures long. "68, long. spir. *18, lat. "3, div. 70. 



A broad sp. '61, '16, '29, 80. 



Hab. Acapulco, Humboldt Sf Bonpland. Panama ; in sand 

 and on mud banks at low water ; Cuming. Do. very rare, 

 C. B. Adams. Mazatlan ; common ; L'pool <$f Havre Coll. 



Tablet 2138 contains 5 sp. pure white 2139, 5 do. slight 

 markings of pink. 2140, 5 do. pink markings stronger. 2141, 

 5 do. well developed. 2142, 5 do. markings fine and close. 

 2143, 5 do. pink passing into olive. 



Tablet 2144 contains 5 sp. white with rare spots of olive.- 

 2145, 5 do. olive spots more developed. 2146, 5 do. with broi 

 white band. 2147, 5 do. olive markings undulating. 21' 

 5 do. zigzag. 2159, 5 do. passing into general olive. 



Tablet 2150 contains 5 sp., undulations absent or very faint ; 

 gray with white spiral band. 2151, 5 do. spiral ; band dar' 

 gray passing towards purple. 2152, 5 do. dark purple. 21 

 5 do. purple changing into olive. 2154, 5 do. lighter. 21 

 5 do. dark olive changing into light. 2156, 5 do. light olive. 



Tablet 2157 contains 5 sp., undulations more or less distinc 

 olive tinged with orange. 2158, 5 do. mai kings light, fai 

 olive. 2159, 5 do. more distinct. 2160, 5 do. distinct. 21i 

 5 do. dark olive. 2162, 5. do. white groundwork appearing. 

 2163, 5 do. white in larger spots. 2164, 5 do. colour darker. 

 2165, 5 do. rich olive. 2166, 5 do. shading into purple. 



Tablet 2167 contains 4 sp. mended after fracture, coloi 

 changing. 2168, 3 sp. shewing variations of form. 2169, 2 

 spiral band varying. (In all, 154 sp. with an appreciable 

 ference between every two.) 



Dad 



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