NO. 10 MOLLUSKS BARTSCH AND REHDER 7 



peristome edged with brown. The whorls increase regularly in size 

 and are marked only by fine incremental lines, excepting the columella 

 which bears 9 rather strong spiral cords, and 7 fine threads near the 

 tip. Aperture ovate, strongly channeled anteriorly ; outer lip thick, 

 bearing 10 elongated denticles having their long axis parallel with the 

 spiral plane. The inner lip partly excavates the columella and parietal 

 wall, leaving it as a smooth porcelaneous surface. There is a humpish 

 callus on the parietal wall near the posterior angle. 



The type, U.S.N.M. no. 472857, has 11 whorls and measures: 

 Length, 13.0 mm.; greater diameter, 5.1 mm.; lesser diameter, 4.4 

 mm. It and a series of specimens, U.S.N.M. no. 472586, were col- 

 lected in Elizabeth Bay, Albemarle Island, Galapagos. U.S.N.M. no. 

 47 2 583 contains 2 specimens collected on Narborough Island, 

 Galapagos. 



This form is much darker than the typical Nitidella guttata Sow- 

 erby, which comes from Panama. 



This is named for Commander C. A. Bailey, Executive Officer of 

 the U.S.S. Houston. 



TRITONALIA (CCINEBRINA) CARIBBAEA, n. sp. 



Plate 1, fig. 1 



Shell small, very elongate-ovate, brown, with the spiral zone of tu- 

 bercles above and below the peripheral keel and the 3 median col- 

 umellar cords white. Aperture brown within with the external white 

 bands marking the peristome ; the denticles within the outer lip are 

 also white. Nuclear whorls eroded. Postnuclear whorls marked by 

 broad low axial ribs, of which 9 are present on the last turn ; strong 

 incremental lines also cross the whorls. The spiral sculpture consists 

 of 3 very strong keels, which grow consecutively stronger from 

 the first at the summit anteriorly. These cords pass across the inter- 

 costal spaces and the axial ribs, rendering these nodulose at their inter- 

 section. The nodules have their long axis coinciding with the spiral 

 sculpture. Lesser spiral threads mark the spiral cords and the spaces 

 between them. Suture moderately strongly constricted. Periphery 

 with a spiral cord as strong as those posterior to it and similarly 

 marked. Base short, well rounded with a heavy nodulose spiral cord 

 on its middle and the finer sculpture noted for the spire. Columella 

 long, somewhat twisted and marked by 2 slender spiral threads near 

 its insertion, followed by 3 heavier cords, then a series of finer, more 

 closely approximated threads near its tip. All this spiral sculpture is 

 rendered roughened by incremental lines. Aperture decidedly chan- 



