DALL: MOLLUSCA AND BRACHIOPODA. 271 



suture deep, appressed ; whorls geutly rounded ; apical whorls with (on the 

 third whorl about fifteen) very narrow, sharp, threadlike, vertical ribs with much 

 wider interspaces, and at the suture numerous, irregular, small, retractive folds 

 extending over the fasciole, with wider interspaces, nearly twice as many as there 

 are ribs ; on the succeeding whorls these ribs and folds grow sparser and weaker, 

 so that on the sixth whorl ribs, folds and fasciole are obsolete or absent ; on the 

 spire, the axial sculpture is crossed by (on the third whorl about eight, on the 

 sixth ten or a dozen) fine flat threads with wider interspaces, (increasing by in- 

 terpolation), which override the ribs and rise above them but do not form nodules 

 at the intersections ; these spirals are very uniform and on the last whorl extend 

 forward covering the canal, and are slightly scored by the incremental lines ; aper- 

 ture oval, not mature in the specimen, the anal sulcus obsolete ; pillar and body 

 polished, the surface erased, not callous ; the pillar is short, gyrate, the axis per- 

 vious, but the canal is short, rather wide, with no siphonal fasciole ; the ouler lip 

 only slightly produced, sharp and thin in the type specimen. Operculum concen- 

 tric, pointed in front, with an apical nucleus. Lou. of (decollate) shell, 23 ; of 

 last whorl, 15 ; of aperture, 10.5 ; max. diam. 7 mm. 



U. S. S. " Albatross," station 2859, in the Pacific Ocean, in 1569 fathoms, 

 ooze, bottom temperature 34°. 9. U. S. N. Mus. 122,590. 



This shell recalls Surculiua, but has harsher sculpture and a large normal oper- 

 culum. It may prove eventually to belong to a group other than Leucosyrinx. 



Irenosyrinx persimilis Dall. 



Plate 13, figrure 3. 



Leucosyrinx persimilis Dall. Proc. U. S. Nat. Mu8., 1889, 12, p. 301, pi. 6, fig. 3. 



Shell large, white, fusiform, with a pale olive periostracum, acute spire, and 

 eight whorls, exclusive of the (lost) nucleus, each carrying a peripheral keel ; 

 suture distinct; whorls behind the periphery somewhat flattened, with a shallow 

 constriction just behind the keel ; axial sculpture only of incremental lines; spiral 

 sculpture between the suture and periphery of numerous flat, subequal, strap-like 

 bauds separated by narrower, shallow channels ; periphery wit h a low, rather 

 wide prominence, giving the effect of a keel and sculptured with several similar 

 but larger, stronger and more distant bands, tending to arrange themselves iu 

 pairs, and with a fine, subsidiary spiral striation upon them ; this sculpture ex- 

 tends over the anterior half of the whorl, l)ecoming finer and closer on the canal ; 

 aperture elongate ; outer lip thin, sharp ; a wide, deep, anal sulcus on the posterior 

 elope of the whorl about midway between the suture and the periphery ; anterior 

 part of the lip arcuate, protractive; body with the sculpture erased, white, 

 polished; pillar short, twisted, in front obliquely truncate and gyrate, but not 

 axially pervious; a touch of brown on the edge; canal wide, elongate, slightly 

 recurved, with no fasciole. Lon. of shell, 95 ; of last whorl, 70 ; of aperture, 55 ; 

 max. diam. of shell, 32 ; of canal, 7 mm. Operculum brown, oval, the exterior im- 

 bricatcly lamellose, the nucleus inside the apical end which is bluntly rounded. 



