2G2 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxiii. 



spiral row of strong tubercles. Channel separating these two rows 

 quite wide. The tubercles are joined axially by low, rather broad 

 riblets, which are decidedly protractive. Beginning with the sev- 

 enth whorl the slender, median spiral thread makes its appearance. 

 This is considerably nearer the posterior keel than the anterior, but 

 in our specimens, which are all young, attains only a moderate 

 development, with extremely weak tubercles. There are about 

 eighteen ribs on the first, twenty upon the second, and twenty-two 

 upon the penultimate post-nuclear turn. Periphery of the last whorl 

 marked by a strong spiral keel. Base excavated without spiral 

 keels covered by the feeble continuations of the axial riblets, which 

 gradually fade out as they approach the short, stout slightly t\\ isted 

 columella. Aperture subquadrate, decidedly channeled anteriorly. 



The type and two additional specimens. Cat. No. 195382, U.S.N.M., 

 were dredged by the steamer Albatross of the U. S. Bureau of Fish- 

 eries, at Station 2813, in 40 fathoms, off Chatham Island, one of the 

 Galapagos Islands. The type has twelve whorls (the first two 

 nuclear probably having been lost) and measures: Length, 3.4 mm.; 

 diameter, 1.2 mm. 



In this form of the aperture and sculpture of the base this species 

 agrees with Triphoi^'is cJiathamensis, but the sculpture of the spire is 

 entirely different. 



EXPLANATION OF PLATE XVI. 



The measurements cited after the name refer to the axial length of the specimen. 

 All the figures have been enlarged six diameters. 



Fig. 1. Trip/ions pfdroan»s, new species; type; 5.1mm. 



2. Tiiphoris peninsularis, new species; type; 4.0 mm. 



3. Tnphoris stearnsi, new species; type; 4.1 mm. 



4. Tnphoris callipyrgus, new species; type; 5.2 mm. 



5. Triphoris galapagensis postalhus, new subspecies; type. 



6. Triphoris inconspicuiis bicolor, new subspecies; type. 



7. Triphoris galapagensis, new species; type; 3.2 mm. 



8. Triphoris excolpus, new species; type; 3.7 mm. 



9. Triphoris chathamensis, new species; type; 2.8 mm. 



10. Triphoris adamsi, new species; type; 3.4 mm. 



11. Triphoris altcrnatus C. B. Adams; type; 4.8 mm. 



12. Triphoris hemphilli, new species; type; 5.1 mm. 



13. Triphoris galapagensis unicolor, new subspecies; type. 



14. Triphoris dalli, new species; type; 6.5 mm. 



15. Triphoris inconspicuiis C. B. Adams; 4.1 mm. 



16. Triphoris carpenteri, new species; type; 7.2 mm. 



17. Triphoris montereyensis, new species; type; 4.6 mm. 



18. Triphoris catalinensis, new species; type; 5.3 mm. 



19. Triphoris panavnensis, new species; type; 8.7 mm. 



