MAZATLAN UNIVALVES 235 
293. OMPHALIUS LIGULATUS, Mzke. 
Trochus ligulatus, Ze7t. f. Mal. 1850, p. 173, no. 34. 
?=Phoreus Californicus, A. Ad. in Proc. Zool. Soc, 1851, 
p. 157, no. 17:—(Omphalius C.) A. & A. Ad. Gen. i. 429. 
{Phorcus, Risso, teste A. Ad. = Omphalius, Phil.: teste 
Piil.=Trochus Magus &c.=Gibbula, Leach, H. & A. Ad.] 
Comp. Phorcus liratus, A. Ad. loc. cit. no. 15 :—(Omphalius L.) 
H. &§ A. Ad. Gen. 1. 429. 
Shell about the shape and size of Phorcus (Gibbula) ciner- 
arius, which takes its place in the Atlantic fauna, as P. umbili- 
caris does that of O. viridulus. Outside crowded with more 
or less fine, more or less subnodulose spiral ridges, of which 
one or more are occasionally more developed than the rest. 
Umbilicus more or less open to the top, where the thin nuclear 
part is generally punctured. Whirls 7, of which the first three 
are smooth and flattened. Mouth slanting: parietal callosity 
near the umbilicus, not projecting; columella between this 
and the spiral ridge deeply sinuated ; spiral ridge ending in a 
broad diagonal callosity, close to which on the labium is a 
small tubercle, and at the base of the shell a large one. The 
area between these tubercles and the layer is rather deeply 
but shortly channeled. From the basal tubercle (in the adult 
shell) runs a callus round the inside of the base of the labrum 
which is sometimes subnodulous. Between this callus and 
the outer lip is a well marked channel. Shell outside covered 
with a rough brown epidermis, conspicuous between the ridges. 
The shell, even when young, is generally covered with Annelids, 
Bryozoa, &e. Colour beneath the epidermis brownish purple, 
or ashy brown, spotted in shades. Operculum outside deeply 
concave, (div. 150°,) of about 20 whirls, not thin, thickened at 
the margin, leaving a distinct suture, not striated; inside 
glossy, of an orange horn colour. A specimen of ordinary 
growth measures long. °69, lat.°77, div. 80°. 
A flattened sp. BANDAS lana (GOs tap 2 
A egnical sp. Rie a ots Seine are 
Hab.—Mazatlan ; common; L’pool Col. 
Tablet 1133 contains 5 sp. whirls somewhat rounded, depres- 
sed.—1134, 4 do. somewhat depressed.—1135, 4 do. typical 
form.—1136, 5 do. conical.—1137, 5 sp. whirls flattened, depress- 
ed.—1138, 3 do. ordinary form. 
Tablet 1139 contains 3 sp. ribs very fine.—1140, 3 do. nodul- 
ous.—114], 2 do. curiously mended after fracture.—1142, 4 do. 
