626 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 117 



Color variation is considerable. The types had a subsutural black 

 or purplish band and the upper spire a series of brownish spots. The 

 body whorl was pale or with subperipheral spiral bands of purple or 

 black. The Sam Roi Yot examples (pi. 2, figs, 3-6) show a wide 

 range of patterning, with yellow, purple, or no subsutural bands, 

 with spots or heavy streaks and sometimes with a yellow green 

 periderm. Basal bands are present on one specimen. The single 

 shell from Srakeo (pi. 2, fig. 2) has an even more modified pattern 

 on the lower whorls with the streaks narrowed, reddish brown, short, 

 and widely spaced. The specimens from Nakon Sritamarat (28.2 mm. 

 high) and Srakeo (31.2 mm. high) are much smaller than the Sam 

 Roi Yot specimens. A juvenile shell from Pran (USNM 419815), 

 Peninsular Thailand, probably belongs to this species. 



Amphidromiis xiengensis Morlet, 1891 



Plate 2 (figs. 7-13) 



Amphidromiis xiengensis Morlet, 1891, Journ. de Conch., vol. 39, pp. 27, 232, 

 240-241, pi. 5, fig. 4 [Xieng Moi Plateau, Laos]. — Laidlaw and Solem, 1961, 

 Fieldiana, Zool., vol. 41, no. 4, pp. 564-565. 



Five color forms could be distinguished in the material examined: 



1. Form xiengensis (pi. 2, fig. 10) has the radial streaks inter- 

 rupted by a single spiral yellow zone and has the streaking continued 

 to (or near to) the aperture. A single adult (37.6 mm. high with 7 

 whorls) from Chiengmai (USNM 420267), North Thailand, is atypical 

 only in having the radial streaking greatly reduced on the last part of 

 the body whorl as in many examples of form clausus. 



2. Form multifasciatus Fulton, 1896, has the radial streaks inter- 

 rupted by several spiral yellow bands with the streaks continuing to 

 the aperture. No adequately localized material of this variation was 

 seen, although the specimen cataloged as USNM 522371, received from 

 Fulton, is possibly a paratype. 



3. From clausus Pilsbry, 1900, has the patterning obsolete at 

 least on the last part of the body whorl, several spiral bands interrupt- 

 ing the radial flames, and a distinctive buff-yellow tone to the portion of 

 the shell without radial pattern. Numerous specimens were seen from 

 Chiengdao (USNM 419906, USNM 420330, USNM 420331, USNM 

 420333) and Doi Hua Mot (USNM 527275) at 1,000 meters elevation 

 in North Thailand. Size variation is summarized in table 1. The 

 umbilicus varies from narrowly to widely open. Of 20 adult shells 

 from Chiengdao, 5 have most or all of the radial pattern reduced or 

 absent, 4 have very little pattern reduced, and the remaining have 

 one or two whorls without radial patterning (pi. 2, figs. 11-13). 



