NO. 1569. WEST A M ERIC A N MOLL USKS—BA R TSCIL 261 



TRIPHORIS CHATHAMENSIS, new species. 

 Plate XVI, fig. !>. 



Shell aciciilar, nuclear whorls light brown, the others white, except- 

 ing the narrow band that connects the tubercles into a spiral series 

 which are brown. Nuclear whorls five, the first smooth, the rest 

 marked by two, quite closely placed spiral threads, the posterior one 

 of which falls on about the middle of the exposed portion of the turns. 

 In addition to the spiral threads the whorls are marked by slender 

 axial riblets, of which there are about twenty-four upon the second 

 and twenty-eight upon the fifth turn. Post-nuclear whorls sepa- 

 ratetl by deep sutures and ornamented from the very beginning by 

 three tubercular spiral keels, of which the median is the most strongly 

 and the anterior the least developed. All the tubercles slope very 

 abruptly posteriorly, which lends them a somewhat truncated appear- 

 ance at this end, and more gradually anteriorly. They are connected 

 axially by slender riblets, of which there are about fourteen on the 

 first, sixteen upon the fifth, and eighteen upon the penultimate post- 

 nuclear whorl. Periphery of the last whorl marked by a slender tuber- 

 culate keel in the immature shell. Base sloping concavely from the 

 keel to the columella; without spiral keels, crossed by the feeble con- 

 tinuations of the axial riblets which gradually evanesce as they 

 approach the columella. Aperture subc|uadrate, irregular, strongly 

 channeled anteriorly, outer and basal lip conforming with the external 

 sculpture and slope, columella short, stout and slightly twisted. 



The type and four specimens. Cat. No. 195381, U.S.N.M., were 

 dredged by the U. S. Fisheries steamer Albatross at Station 2813, in 

 40 fathoms off Chatham Island, one of the Galapagos group,. They 

 are immature. The type has twelve whorls and measures: Length 

 2.8 mm.; diameter, 1.1 mm. 



This is one of the most distinct forms known to us at present from 

 the entire coast; the presence of the three spiral keels from the very 

 beginning is a character possessed by only one other form, namely, T. 

 callipyrgus from San Pedro, California, which is a much larger species 

 with three basal keels. 



TRIPHORIS ADAMSI, new species. 



Plate XVI, fig. 10. 



Shell acicular, uniformly yellowish wdiite. Early nuclear whorls 

 decollated; the three remaining are marked by the characteristic 

 sculpture, the double spiral thread, the posterior one of which is 

 upon the middle of the whorls, and many slender, axial riblets, of 

 which there are about twenty-four upon the last turn. Post-nuclear 

 whorls increasing very regularly in size, ornamented with a double 



