DALL: MOLLUSCA AND BRACHIOPODA. 297 
convex ; axial sculpture of numerous (on the penultimate whorl about twenty) low 
rounded ribs, with shallow, subequal interspaces, strongest at the angle, obsolete 
on the tabulation and on the last whorl, extending on the spire to the succeeding 
suture; the incremental lines are also rather conspicuous; spiral sculpture in front 
of the angle of (on the spire about four, on the last whorl about twenty) low 
rounded subequal spiral threads with wider interspaces, a little turgid where they 
cross the ribs, especially on the spire, and more crowded on the last whorl, anteriorly, 
where they extend to the brink of the umbilicus; aperture subtriangular, the outer 
lip thin, not reflected; body with a thin wash of callus; pillar thin, straight, with 
three plications, the middle one strongest; canal obsolete or none; umbilicus rather 
large, funicular, its walls vertically striate, the opening partly concealed by the pil- 
lar lip; in the young the umbilicus is relatively much smaller; operculum absent. 
Length of shell, 16; of last whorl, 11; of aperture, 8; max. diam. 8.3 mm. Length 
of figured specimen, 10 mm. ; 
U.S. 58. “ Albatross,” station 2980, in 603 fathoms, mud, bottom temperature 
39° F. U.S. N. Mus. 110,626. Also at stations 3346, 3194, 2889, 2923, 2936, 
and 4339, from off Tillamook Bay, Oregon, south to the vicinity of San Diego, 
California, in from 92 to 786 fathoms, temperatures from 37°.3 to 49° F. 
The specimen figured, from 2936, is about two-thirds grown; the others were 
discovered later. It does not show the third feeble plait, nor the somewhat sud- 
den enlargement of the last whorl, both noticeable in the fully adult shell. It has 
the aspect of an Admete, in spite of the presence of an umbilicus, but is perhaps 
only a delicate form of Trigonostoma. 
Volutidae. 
CARICELLINAE. 
ADELOMELON Datu. 
Adelomelon Dall, Nautilus, April, 1906, 19, p. 143; type Voluta ancilla Solander; 
Smithsonian Misc. Coll. Quarterly, 1907, 48, p. 3855. 
In making a thorough and too long delayed examination of the systematic his- 
tory of the Volutidae, in connection with a revision I have been making of the 
group, I discovered that the type of the genus Scaphella (under which I had 
formerly included the dull-colored American group of Volutes) is V. undulata, 
which belongs to the group of which Amoria Gray is a synonymic name; and the 
type of Cymbiola Swainson, which has been used for them by several authors, is 
Voluta vespertilio Linné. Both of these forms have a shelly protoconch, and be- 
long to another subfamily. Scaphella has a peculiar brilliant surface enamel 
which no American Volute possesses, and a totally different radular dentition. It 
is obvious, therefore, that neither of these groups can properly contain the Ameri- 
can shells which form an extremely natural group, and to which I have given the 
name of Adelomelon. 
