256 MAZATLAN UNIVALVES 
spiral ribs, a taller spire, and a yellow mouth. These charac- 
ters do not always go together, and are each extremely variable, 
as are also the ruge on the columellar lip, it being difficult to 
find two specimens exactly alike. The fineness of the ribs 
sometimes differs in different parts of the same shell. The 
colour within presents all shades from a brilliant orange to pure 
white. The sharp labral margin, (crenulated by the ribs,) is 
either black throughout, or tessellated with light between the 
ribs. Spire always more or less eroded, even in young speci- 
mens, which in this collection were extremely rare. These are 
known from the next species by the non-granular lip (smooth 
in the youngest specimen,) strong teeth, and raised spire. 
Coste often scarcely scabrous. Labrum thickly callous within 
the margin, dentate, with very strong teeth at the extremities. 
Ruge often continued on the spire, beyond the flattened colu- 
mella. Operculum (in both the forms N. ornata and N. 
Deshayesii) outside finely granular, with an obscure spiral line 
marking off about a quarter of the shell from the outside, and 
ending in a deep sinus on the inner margin. ‘Tooth stoutly 
projecting, curved downwards opposite the not inconspicuous 
spiral apex. Colour orange brown. A few were found loose, 
with the spiral line searcely developed, and of a more ashy 
colour. As there was no other large species of Nerita among 
the shells, these are presumed to be of abnormal growth. The 
following shells, selected from but a small stock, exhibit the 
principal variations in the wrinkling near the second of the 
four teeth: to display all the minute differences would have 
been to retain almost every specimen. ‘The shells are not 
nearly so large as further down the coast ; the largest measur- 
ing only long. 1°11, lat. 1°18, div. 110°—120°. 
Hab.—\s. of Timor; sp. typ. Lam. teste Recluz. [?]—Real . 
Llejos, Sowerby.—Panama ; very common, on rocks, especi- 
ally in crevices, between high water and three-quarter tide ; 
young crawling above high water mark on rocks and stones 
wet with spray; C. B. Adams.—S. W. Mexico, P. P. C.— 
Mazatlan ; not common; L’pool & Havre Coll. 
Tablet 1181 contains 4 sp. of different ages: the smallest, 
‘AS across, displays an orange spire, smooth at the apex, with 
distant ribs, intercalary ones appearing at the margin.—1182, 
1 sp. ribs distant, form ornata.—1183, 1 do., ribs changing, in 
part very close, form Deshayesii.—1184, 2 sp. displaying col- 
oured lip; one with a single orange spot, the other richly 
tinted, inside and out, with spire abnormally elevated. 
