BALL : MOLLUSC A AND BliACHIOPODA. 345 



and spongy, outside of this ridge in tlie 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 multispiral, 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 fathom^ 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 Mazatlaa and the Gidf, as well as the 

 coast of Alta California. 



Liotia (Arene) pacis Dall, n. ep. 



This species is so similar to the preceding that it is best described by a com- 

 parative diagnosis. 



Thau L. 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 iuto 

 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. S. "Albatross," station 2996, off La Paz Bay, Lower California, in 112 

 fathoms, mud, bottom temperature 56" F. U. S. N. Mus. 110,663. 



Trochidae. 



CLANCULrs MoNTFORT. 



Pauococlilea Dall, 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 



