DALL: MOLLUSCA AND BRACHIOPODA. 287 
is more or less constricted ; at the shoulder begin about fifteen short, very ob- 
liquely protractive, wave-like ribs, with narrower interspaces, which are con- 
spicuous only near the periphery; surface otherwise smooth except for faint 
incremental lines; aperture lunate ; anal sulcus wide, shallow; outer lip sharp, 
thin, arcuately produced in front of the suleus; body polished; pillar short, 
gyrate, not pervious, obliquely truncate in front; canal very short, wide, and 
slightly recurved. Lon. of shell, 10.5; of last whorl, 6.5; of aperture, 5.0; 
max. diam. 4.6. mm. Operculum none. 
U.S.S. “Albatross,” station 3392, Gulf of Panama, in 1270 fathoms, hard 
bottom, temperature 36°.4 F. U.S. N. Mus. 123,131; and station 3393, in 
1020 fathoms, mud, temperature 36°.8 F. U.S. N. Mus. 123,122. 
This and the preceding species are not of the typical group of Mangilia, having 
more the profile of a Gemmula with a short canal, or a small, slender, high-spired 
Gymnobela, but they are left here for the present, pending a revision of the entire 
group. 
Mangilia sedillina Datt, n. sp. 
Plate 13, figure 8. 
Shell small, translucent white, very thin, fusiform, the nucleus eroded, with 
four subsequent whorls; suture distinct, whorl in front of it with a narrow, thick- 
ened margin ; whorls slightly angulated at the shoulder, the angle obsolete on 
the last whorl; axial sculpture, in addition to lines of growth of (on the penulti- 
mate whorl abcut twenty-six) fine, sharp, narrow lamellose riblets following the 
lines of growth, beading the presutural band, angulated at the shoulder and obso- 
lete on the base, with wider, excavated interspaces ; these are crossed by very 
numerous, fine, close-set, spiral threads, slightly coarser on the canal and 
minutely feebly reticulated by the incremental lines; body and pillar polished, 
the sculpture erased; outer lip thin, simple, with a wide sulcus occupying the 
space between the suture and the shoulder, in front of which it is arcuately pro- 
tractive; pillar straight, simple, obliquely truncate in front; canal short, wide, 
not recurved. Operculum absent. 
Variety with stronger sculpture, shorter and stouter shell, and distinctly re- 
curved canal. 
Lon. of (decollate) shell, 8.0; last whorl, 6.7; aperture, 5.0; max. diam. 
4.0 mm. Same dimensions in the variety, 5.7, 4.5, 4.0, and 3.5 mm. 
U.S. S. “ Albatross,” station 3392, Gulf of Panama, in 1270 fathoms, hard 
bottom, temperature 369.4 F. U.S. N. Mus. 123,116 and 123,116 a. 
Mangilia encella Dat, n. sp. 
Plate 14, figure 11. 
Shell small, white, with a translucent thin periostracum and about five whorls 
(the nucleus eroded); spire slightly longer than the aperture; early whorls 
rounded with about fifteen slender, low, arcuate, protractive, axial riblets which are 
