486 MAZATLAN UNIVALVES 
The true M. vitulinus, Zam. appears to be an African shell, 
closely resembling but distinct from the very variable species 
of Ww. America. The Mazatlan specimens are very rarely 
white, or banded with purple brown; but almost always of an 
auburn tint, especially at the border of the mouth, which is 
white within. Shape generally with the spire moderately 
elevated, sometimes turrited, sometimes depressed and pyri- 
form. Upper whirls angular, generally flattened, with regular 
varicak ridges asin Trophon. Nuclear whirls smooth, turrited, 
fixed slanting, deciduous. Normal whirls scabrous, generally 
developing a row of obtuse nodules on the shoulder, which some- 
times elongate into faint cost. Varices foliaceous, extremely 
irregular, rarely seen on the spire, from one to six on the last 
whirl, at variable distances. Labium smooth, with an infra- 
sutural tooth as in Pisania. Canal more or less elongate. The 
creature appears to be of sluggish habits, being frequently 
worm eaten, and encrusted with Bryozoa, &c. though not with 
coralline. It is very rarely pierced by Lithophagus and Gas- 
trochena. The operculum is diamond-shaped, with two short 
sides above, and two long ones below, angles rounded : outside 
with ridges of growth; inside with a very large muscular scar, 
reddish, corrugated, with a few lines of growth; a loose yel- 
lowish border is seen round the outer edge. The largest sp. 
measures long. 3°84, ‘long. spir.1°4, lat.2°1, div. 60°. 
An elevated sp.,, 3°84, ‘ 1°98: oe bSe 2 ee: 
A pyriform sp. ,, 2°95, ‘ Fie. (cil decerpr Ou. 
Hab.—S. America, Sowerby, Deshayes.— Panama; under 
stones, not far from low water mark; C. B. Adams.—Maz- 
atlan; not uncommon; L'pool & Havre Coll. 
Tablet 2287 contains 4 sp. adolescent.—2288, 3 sp. single 
varix, depressed.—2289, 3 do. normal.—2290, 2 do. elevated.— 
2291, 3 sp. with 2 varices, depressed.—2292, 2 do. normal.— 
9293, 2 do. elevated.—2294, 3 sp. normal, varices 3 or more.— 
2295, 2 do. elevated varices 3 or 6.—2296, 4.sp. shewing changes 
of colour.—2297, 3 do. shewing extremes of sculpture.—2298, 
1sp. elongated canal.—2299, the largest sp., stout columellar 
callosity, apparently deposited as a guard against worms.— 
2300, an elongated sp. with a similar callosity.—2301, a sp. with 
fresh canal, after fracture, bent as in Cassidaria.—2302, a sp. 
which, in mending a hole between two varices, has protuded a 
second lip, with a passage to the inside (as in Trochotomus.)— 
2303, 3 separate opercula. The youngest sp. in tablet 2287, 
and one in tablet 2297 have their opercula im situ. 
