DIAGNOSES OF NEW SPECIES OF MOLLUSKS FROM THE 

 WEST COAST OF AMERICA. 



By W. H. Ball, 



Honorary Ctirator of ilie Department of Molhisks. 



During the work of the Albatross on the west coast of America a 

 number of iuteresting species new to science have been collected, some 

 of which have been described and illustrated, but many more still 

 remain to be worked up. Pending the completion of studies now in 

 progress the following diagnoses of especially iuteresting forms are 

 printed, to attract attention to certain groups not hitherto discrimi- 

 nated. 



CALLIOSTOMA IRIDIUM, new species. 



Shell thin, with pearly sheen; conical, with eight whorls; nucleus 

 smooth, polished, bulbous, asymmetrical, of less than one whorl; sub- 

 sequent whorls flattened, so that the sides of the spire are nearly 

 straight, diverging at an angle of 00°, and sharply angular at the 

 periphery, against which the suture is laid; base flattisli, near the 

 aperture more or less rounded, imperforate; sculpture on the spire of, 

 first, a strong thread, bordering the suture on each side, this thread 

 separated by a channel from the flattened area between the two threads, 

 upon which area are (on the last whorl seven) spiral threads, which on 

 the last whorl are beaded and separated by wider interspaces, above 

 become fainter or lose the beading, are obsolete on whorls 4, 5, and 6, 

 while on the apical whorls only the strong threads remain; the latter 

 are also beaded on the later whorls; base spirally threaded, the threads 

 more or less beaded by the intersection with them of arched, rather 

 strong radiating lines of growth; threads stronger and more distant 

 as they ajiproach the smooth, broad axial rib; the periphery of the last 

 whorl with two granulated keels; aperture subcjuadrate, brilliantly 

 pearly, the pillar white, smooth, with no tooth or projection at its base; 

 color of the shell pinkish waxen, verging toward bluish near the apex, 

 with variable delicate brown flammules, which cross or variegate the 

 whorls and usually end as more or less distinctly paired brownish spots 

 on the periphery of the last whorl, not being visible on the base: the 



Proceedings of the United States Isatioual Museum, Vol. XVIII— No. 1034. 



