MAZATLAN UNIVALVES 469 



596. OLIVELLA TERGINA, Duel. 



Oliva tergina, Dud. Man. Oliv. p. 7, pi. 2, f. 13, 14. Wee. in 



Zeit.f. Hal. 1847, p. 183, no. 24 : do. 1851, p. 25, no. 107. 



Eve. Conch. Ic. pi. 26, f. 80. 

 Olivella tergina, H. fy 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 sufficiently 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 a rich purplish brown, and are sometimes 

 absent altogether. The dried animals, which were abundant 

 and easily softened, gave no token of opercula. The West 

 Indian analogue is O. conoidalis. An acuminated specimen 

 measures long. '72, long. spir. '33, lat. "28, div. 50. 



A broad sp. '66, '29, '32, 50. 



The difference of divergence is in the later, not the earlier 

 whirls. 

 Hob. Conchagua ; on sand banks ; Cuming. Mazatlan ; in 



extreme profusion ; Z/'pool fy 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 

 grey. 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, Dud. 



Oliva anazora, Dud. Hon. Oliv. pi. 5, f. 3, 4. MJce. in Zeit. 



f. Hal. 1851, p. 25, no. 106. Eve. Conch. Ic. pi. 25, f. 74. 

 Olivella anazora, H. fy 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 



