DALL: MOLLUSCA AND BRACHIOPODA. 319 
Bolten’s group was divided into two sections, one containing species of Dis- 
torsio (with oné not dissimilar form Triton tuberosum Lamarck); the second con- 
tainmg Lamarckian Nassas of the NV. arcularia group, which were afterward 
separated by Link as a distinct genus, Arcularia, which he credits to Bolten, 
though the name does not occur in Bolten’s posthumously published system. 
Link was in the habit of changing the desinence of names which did not please 
him, and his Distortrix was one of these to which he places Distorsio Bolten, as 
a synonym, minus, of course (as he indicates later) the Arcularia group. The 
question, therefore, arises: are we to regard Distortrix and Distorsio as two 
things or one? At first I thought we could use both, and so in 1904 (Frogshells 
and Tritons, p. 133) retained Distortrix, thinking Distorsio might be retained for 
the remnant; but, after more mature consideration, I believe this was incorrect 
and that, following Tryon, we should adopt Distorsio in its original form, and 
regard Distortrix as an absolute synonym thereof. 
If we do not do so, but proceed by elimination, Distorsio will supplant Guttur- 
nium Morch as a designation for the ‘‘ Tritons ” of the tuberosum group. 
Distorsio decussatus VALENCIENNES. 
Triton decussatum Valenciennes, Humboldt Voy., 1833, 2, p. 806; Reeve, Conch. 
Icon., 1844, Triton, pl. 12, fig. 41. 
U. 8. 8. “ Albatross,” station 3355, Gulf of Panama, in 182 fathoms, mud, 
bottom temperature 54°.1 F. U.S. N. Mus. 123,026. 
TRITONOHARPA Datt, nov. 
Shell recalling Hoctthara in shape, with a simple suture, the whorls axially 
ribbed and at intervals varicose, varices not continuous up the spire; surface with 
minute velvety sculpture; aperture with the peritreme elevated and continuous 
behind, the inner lip smooth, with the outer margin of the callus detached from 
the whorl; outer lip denticulate, varicose at resting stages; canal proximally 
more or less constricted, narrow, produced, and recurved; throat not lirate. 
Operculum ? 
Type, Tritonoharpa vexillata Dall. 
This peculiar little shell has refused to be suitably placed in any known genus. 
The aperture is unlike that of any form of Cymatium known to me, and, in thie 
absence of the soft parts, it is only referred provisionally to the Septidae. The 
sculpture recalls that of Harpa in miniature, except that the ribs do not spread 
over the suture and the varices stand out vertically from the surface. The dentic- 
ulate outer lip recalls some forms of Cassis and the thin outer sculptured layer of 
shell forms a surface not unlike, in texture, that of Cassis cameo Stimpson. But 
none of the Cassididae has a continuous raised lamella without sculpture behind 
the aperture. If Mayer’s genus Silia possesses in reality the characters allotted to 
