DALL: MOLLUSCA AND BRACHIOPODA. 345 
and spongy, outside of this ridge in the young it is constricted by a row of pits 
between which and the periphery are some obscure spirals in some specimens ; 
aperture circular within, and when fresh brilliantly pearly, but the pearly coating 
is very thin and seems to disappear in dead shells ; the outer margin of the aper- 
ture, which is very thick, is modified by the umbilical keel and other sculpture ; 
operculum wmultispiral, with the external edges of the whorls fringed, very con- 
cave, and showing hardly any calcareous deposit. Alt. of adult, 15.0; of aper- 
ture, 9.0; max. diam. 23.0; min. diam. of base, 15.0; umbilicus, 3.0 mm. 
U. S. S. “ Albatross,” station 2984, off Lower California, in 113 fathoms, sand, 
bottom temperature 49°.8 F. U.S. N. Mus. 110,662. 
This species is usually covered with Polyzoa, Lithothamnion, and other 
adherent matter, which obscures its appearance, but the shell itself is so rude, 
spongy, and bleached in appearance that the actual surface is often discriminated 
only when examined with a lens. It is the largest species of its group and the 
first to be reported from the region, though there are several small species of 
typical Liotia named by Carpenter from Mazatlan and the Gulf, as well as the 
coast of Alta California. 
Liotia (Arene) pacis Da tt, n. sp. 
This species is so similar to the preceding that it is best described by a com- 
parative diagnosis. 
Than LZ. californica it is smaller, flatter, and more distinctly sculptured; the 
specimens examined have three and a half whorls beside the (lost) nucleus ; it 
has eight peripheral projections instead of six, and they are flat, triangular, and 
spinose instead of bluntly tubercular ; each projection is at the distal end of a dis- 
tinct radial rib; the base is flatter, the umbilical ridge lower, and broken up into 
obliquely radial tubercles without any row of pits outside of it; the aperture is 
subcircular and the discrepancy between the inner and outer margins much less 
than in californica. Alt. of shell, 10.0; of aperture, 6.0; max. diam. of base, 
15.0; min. diam. 11.0 mm. 
U.S. 8. “Albatross,” station 2996, off La Paz Bay, Lower California, in 112 
fathoms, mud, bottom temperature 56° F. U.S. N. Mus. 110,663. 
Trochidae. 
CLANCULUS Montrort. 
Panocochiea Datt, subg. nov. 
Shell depressed-conic, aperture very oblique, the outer lip produced at the 
periphery; a single, strong tooth at the end of the pillar with a sulcus in front of 
it, a layer of smooth enamel, continuous with that of the outer lip, spread over 
the umbilical region (which is without pit or perforation) and a large part of the 
