BALL: MOLLUSCA AND BRACHIOPODA. 319 



Bolten's group was divided into two sections, one containing species of Dis- 

 torsio (with one not dissimilar form Triton, tuberosum Lamarck) ; the second con- 

 taining Lamarckian Nassas of the N. 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. 306 ; Reeve, Conch. 

 Icon., 1844, Triton, pi. 12, fig. 41. 



U. S. S. " Albatross," station 3355, Gulf of Panama, in 182 fathoms, mud, 

 bottom temperature 54°.l F. U. S. N. Mus. 123,026. 



TRITONOHARPA D.\ll, nov. 



Shell recalling Eocithara 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 

 behiud, the inner lip smooth, with the outer margin of the callus detached from 

 the whorl ; outer lip denticulate, varicose at resting stages ; canal proxinially 

 more or less constricted, narrow, produced, and recurved ; throat not lirate. 

 Operculum ? 



Type, Tritonohtrpa 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 mc, and, ni tlie 

 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 tlio 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 



