232 MAZATLAN UNIVALVES 
Comp. Trochus eximius, Rve. Proe. Zool. Soe. 1842, p. 185. 
(Payana, sandy mud, 10 fm. Mus. Cuming.) 
This beautiful species is characterized in sculpture by a more 
or less sharp angular keel, at about 3-5ths of the breadth of 
the penultimate whirl, the whole surface being covered with 
very fine subgranular spiral striz ; basal periphery at a rounded 
angle; base with about 9 distant, nearly smooth and scarcely 
raised strie. Colouring variegated with ashy and light orange 
brown, very rarely wholly of a rufous tinge, stained about the 
granules and on the basal lines with lustrous purplish red, also 
with rich orange. The first whirl is depressed, smooth, round- 
ed; gradually passing into very coarse decussation, leaving 
deep pits between; these pass into three strongly nodulous 
ribs, the lower gradually changing into a keel, small ones 
developing between the others, and both nodules and ribs 
gradually subsiding into the typical state. The young shell is 
of a uniform orange brown or reddish tinge. Whirls 10. Very 
few specimens possessed the operculum, which is extremely 
thin, of many whirls (15 in a shelk of 9 whirls,) with very 
delicate radiating strie, somewhat curved, and most developed 
near the margin of each whirl. Zong. 1°, lat. °92, div. 65°. 
Hab.—Mazatlan ; common; L’pool & Havre Coll. 
Tablet 1118 contains 4 sp. various ages.—1119, 2 sp. extreme 
forms, div. 60°-80°.—1120, 5 sp. shewing base and variations 
of sculpture.—1121, 2 sp. with hermit crabs.—1122, 1 sp. with 
operculum. 
Specimens shewing colowr.—1123, 4 sp. dark, variegation in 
large pattern.—1124, 3 do. with narrow streaks of hght.—1125, 
3 do. nearly uniform, dark.—1126, 3 do. light and dark equal.— 
1127, 3 do. light predominating.—1128, 3 do. nearly uniform, 
hight. 
290. Trocuus Mac-ANDRES, 2. Ss. 
T. t. subelevatd, conicd, anfractibus convexiusculis, sutura dis- 
tinctéd ; rubra, maculis pallidioribus : livis sptralibus nodosis 
cincta, in anfr. penult. vi. quarum inferiores due paullum majores 
sunt ; interstitiis impressis, lirulis interdwm intercalantibus ; 
tuberculis confertis, rotundatis, extantibus ; peripheria vie an- 
gulaté; basi lirulis vix granulosis, circiter xi. ornatd, inter- 
stittis latis ; coluwmellé haud insculpté, parum contortd, regione 
umbilicali impressa. 
Var. t. rufo-fuscd, undatim pallidiore ; bast rubro. 
