MAZATLAN TNIA'ALVES 331 



and clianging to another. The adolescent portion is generally 

 swollea, of smoother growth ; the adult with the whirls irregu- 

 lar, more or less drawn out, and frequently with sharp ridgea 

 of growth behind the labrum. But whatever condition the 

 adult maj' assimie, the young thell always has one sharp spiral 

 keel in the middle of each whirl, surrounded by spiral stria. 

 The operculum is of uniform coloiir, with about 18 whirls ; 

 with one row of sharp tubercular hairs next the suture, and 

 other more stimipy ones following ; with a veiy fine border, 

 radiately striated, followed by a long hairy fringe. The 

 youngest sp. has five whirls, of which the first two are smooth. 

 It measures 'OlS by "028. An adolescent specimen (12 whirls) 

 measures lonff. 2'07, long. S2nr.l'64i, Jat. '74, Jiy. 22°. 



The largest (17 whirls) 4-5, „ 3- 88, „ '98, „ 10». 



Aslendersp.(15whirls)3'7, „ 3-2, „ "82, „ 8". 



Mab. — Acapulco, Humboldt Sf Bonplancl. — Panama, Kiener. — 



Payta, Salango, Guacomayo ; in sandy mud, 5 — 10 fm. ; 



Cuming.—^. W. Mexico, P. P. C— Mazatlan ; not uncom- 

 mon ; L'pool Col. 



Tablet 1552 contains 6 sp. extremely yoimg. — 1553, 2 sp. 

 young ; one passing from chalcedony to purple brown, then 

 suddenly to nearly white, then gradually to dark, linear 

 pattern. 



(1.) Tablet 1554 contains 2 sp. uniform purple black ; one, 

 whirls flat, the other rounded. — 1535, 2, sp. very dark, tinted 

 with orange brown.— 1556, 2 sp. black purple ground, slightly 

 variegated with white. — 1557, 3 do. normal state, with more 

 white ; one has passed through acid, to display colour. — 1558, 

 3 do. purijle, light aliounding ; one in dashes above, clouded 

 below ; another with both large and small pattern. — 1559, 3 do. 

 light predominating ; brownish purple in clouds, dashes or 

 spots. 



(2.) Tablet 1560 contains 3 sp. dark olive brown, with piirple, 

 linear pattern or variegated. — 1561, 2 do. white abounding. — 

 1562, 3 do. light tint, linear markings conspicuous. 



(3.) Tablet 1563 contains 1 sp. purple brown passing into 

 orange brown. — 1564, 2 sp. nearly uniform orange brown ; one 

 nearly smooth, with blunt shoulder keel; the other rough, 

 keeled above and below.— 1565, 3 do. with faint purple brown 

 cloudings ; one very slender, lower whiils separating.— 1566, 

 2 do. lower whirls passing into normal colouring. — 1567, 2 do. 

 upper half of the whirls richly variegated. — 1568, 3 do. light 

 predominating ; pattern clouded or dotted. 



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