LAND SNAILS FROM THAILAND — SOLEM 617 



A. xiengensis, A. areolatus, and A. semitessellatus. Typical examples 

 were immediately separable, but several sets were examined that 

 were exceedingly difficult to allocate. What I have called A. areolatus 

 is relatively small (23-28 mm. high) with a closed to moderately 

 open umbilicus, thin shell, usually a reddish columellar patch, and 

 brown and yellow spiral zones on the base of the shell, A. semitessel- 

 latus is a larger (28-39.5 mm. high), much thicker and heavier shell, 

 with the columella nearly straight, and the basal portion of the 

 aperture sharply rounded or actually angulated, the umbilicus closed 

 or a narrow chink, with purple, yellow, or no subsutural bands, and 

 only medial interruption of the radial streaks (when present). A. 

 xiengensis is usually a large (30-39 mm. high) shell with a red sub- 

 sutural line, narrowly to widely open umbilicus, columella curved 

 and basal margin of aperture broadly rounded; the radial streaks 

 (when present) interrupted by one to several spiral zones. Shells 

 from Kao Sabab, tentatively referred to A. xiengensis, are smaller 

 (27.5-34.3 mm. high), lack the red subsutural band, have a more 

 sharply rounded basal margin of the aperture, but show the xiengensis 

 color pattern. Another set from Kao Pae Nam have the size, 

 subsutural line, and radial streaks of A. xiengensis, but the columellar 

 patch and aperture of A. areolatus. It is tentatively grouped with 

 A. xiengensis. 



While sets of A. xiengensis, A. semitessellatus, and A. areolatus are 

 usually readily separable, single specimens or short series of worn shells 

 are difficult to identify. As indicated below, each species has a 

 typical color pattern, but individual variations with almost complete 

 loss of color pattern occur in each species. The demonstrated oc- 

 currence of dwarf ecotypes in Amphidromus prevents size criteria 

 from being utilized as a distinguishing feature. Probably a combina- 

 nation of ecological, anatomical and conchological studies will be 

 necessary before the relationship of the various forms can be accurately 

 determined. 



The Thailand shells are listed in the same seq'uence used by Laidlaw 

 and Solem (1961). 



Amphidromus sinensis var. indistinctus Pilsbry, 1900 



Plate 1 (fig. 10) 



Amphidromus sinensis var. indistinctus Pilsbry, 1900, Man. Conch., ser. 2, vol. 13, 

 p. 192, pi. 62, fig. 70 [mountains of Laos]. — Laidlaw and Solem, 1961, 

 Fieldiana, Zool., vol. 41, no. 4, p. 523. 



Two adult shells from Ban Nam Kien (USNM 405863) and Ampur 

 Chiengdao (USNM 420332), North Thailand, are unquestionably 

 this form. They are, respectively, 35.7 and 35.1 mm. high, h/d 



